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English Grammar Step by Step: • Contents
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Gramática inglesa de nivel medio paso a paso (Intermediate English Grammar Step by Step)


     UNIDAD 4


   Rellene los espacios en blanco según corresponda.


1. Los verbos have to y must expresan obligación. Must sugiere que la obligación proviene del hablante; have to, de una autoridad externa o de las circunstancias. No obstante, en ocasiones se emplea must en vez de have to para indicar que, aunque la autoridad es externa, el hablante está de acuerdo con ella. Véamos a continuación unos ejemplos para ilustrar esto:
   You must be at home before it gets dark. (Tienes que/Debes estar en casa antes de que anochezca. » Esto se lo diría una madre o un padre a su retoño.)
   I have to get up at five o'clock in the morning to go to work. (Tengo que levantarme a las cinco de la mañana para ir a trabajar. » La idea de madrugar no me hace ninguna ilusión, pero he de ganarme la vida.)
   You must/have to follow the doctor's advice. (Tienes que/Debes seguir el consejo del médico. » Have to implica que yo no lo impongo; must, que, pese a no ser decisión mía, comparto la opinión del médico.)

a  I __________ go home on foot: no means of transport can take me there.
b  He __________ work twelve hours a day to maintain his family.
c  We __________ leave now. We've got lots of things to do.
d  She __________ be here by midnight, or else I'll punish her.
e  You __________ give up smoking. You're always coughing!


2. Lo contrario de must es need not; de have to, do not have to1. Sin embargo, también se puede emplear do not have to en lugar de need not.
   You needn't/don't have to read all the book. The first two chapters will be enough. (No hace falta que leáis todo el libro. Con los dos primeros capítulos será suficiente.)
   I don't have to get up early tomorrow, as it is Sunday. (No he de levantarme temprano mañana, puesto que es domingo.)

a  He __________ (not) work. His wife is very rich.
b  You __________ (not) take me there. My mother can do it.
c  You __________ (not) buy us a present. You're very short of money.
d  You __________ (not) take your car. You can go in mine.
e  They __________ (not) come if they don't want to.


3. Must y need not carecen de la mayoría de formas verbales; por eso, have to y not have to, respectivamente, son necesarios cuando must and need not son imposibles.
   We must hurry: it is getting late. (presente » Debemos darnos prisa: se está haciendo tarde.)
   We must visit our parents tomorrow. (futuro » Tenemos que visitar a nuestros padres mañana.)
   We will have to visit our parents tomorrow. (futuro » autoridad externa » Tendremos que visitar a nuestros padres mañana.)
   We had to hurry, as it was getting late. (pasado » Tuvimos que darnos prisa, dado que se hacía tarde.)
   He needn't pay me for that. (presente » No hace falta que me pague por eso.)
   She needn't come tomorrow. (futuro » No es necesario que venga mañana.)
   He didn't have to pay me for that. (pasado » No hacía falta que me pagara por eso.)
   She didn't have to come the next day. (pasado » No era preciso que viniera al día siguiente.)

a  I know that yesterday you __________ be at home before it got dark.
b  We __________ (not) go to school yesterday, so we went for a picnic.
c  I __________ study all night long yesterday because I wanted to get top marks.
d  We __________ (not) ask their advice, since Martha was there and helped us.
e  Our troops __________ retreat. Our soldiers are falling like flies.


4. Must not2 implica que algo no se debe hacer porque está prohibido o porque traería resultados adversos o funestos:
   You mustn't eat all that. It's very spicy and hot. (No debes comerte todo eso. Está muy condimentado y es muy picante.)
   You must not overtake. There is a continuous line here. (No debes adelantar. Hay línea continua aquí.)

a  You __________ (not) drive so fast. This road is very dangerous.
b  You __________ (not) drink more. You have to drive.
c  You __________ (not) arrive late for your interview.
d  They __________ (not) make any comments about this.
e  She __________ (not) forget to switch the light off when she leaves.


5. Should3 significa "deberías", y se usa para consejos. Must es posible en vez de should cuando el consejo es enfático.
   You should cut down your expenses. (Deberíais reducir los gastos.)
   You must visit Barcelona. It's the best city in the world. (consejo enfático » Tienes que visitar Barcelona. Es la mejor ciudad del mundo.)

a  You __________ see this film. It's extremely good.
b  You __________ tell them what happened.
c  He __________ take evening classes. They will do him some good.
d  You __________ listen to this record. You'll love it.
e  You __________ come to the party with us. You'll enjoy it very much.


6. Need not have + participio de pasado4 se usa para indicar que se hizo algo innecesario:
   You needn't have taken a bus. You could have gone in my car. (No tenías por qué haber cogido un autobús/No era necesario que hubieses cogido un autobús. Podrías haber ido en mi coche.)

a  You __________ (not) have brought anything. There is plenty of food in the house.
b  We __________ (not) have sent them a letter. They will be here tomorrow.
c  He __________ (not) have paid for the ticket. I have one spare ticket.
d  She __________ (not) have bought that book. I could have lent her mine.
e  They __________ (not) have read the whole novel. They only had to read the first three chapters.


7. Cuando tenemos suficientes indicios para creer que algo es cierto, utilizamos must. Lo contrario de must es cannot.
   They must be filthy rich because they have their private jet. (Deben de ser asquerosamente ricos porque tienen un jet/avión privado.)
   They cannot/can't have a Rolls-Royce. They are very poor. (Es imposible que tengan un Rolls-Royce. Son muy pobres.)
   You must have had5 a great time in Eivissa. (Tienes que habértelo pasado en grande en Eivissa.)
   You cannot/can't/could not/couldn't have seen a vampire last night. Vampires don't exist! (Es imposible que vieras un vampiro anoche. ¡Los vampiros no existen!)

a  There __________ be a mistake in the bill. It __________ (not) cost so much. You told me it was very cheap.
b  They __________ (not) have fired him. He's been working for them for over twenty years.
c  You __________ (not) be serious! You __________ be joking!
d  You __________ (not) have seen him smoking. He detests it.
e  If you haven't eaten anything since yesterday, you __________ be very hungry.


8. Ejercicio de revisión.
a  My father __________ work overtime to support us when we were children.
b  We __________ help our parents when they were ill.
c  You __________ (not) have bought any roses. There are lots in the garden.
d  You __________ (not) worry about this illness. It's under control.
e  He __________ come last night. We needed him.
f  You __________ (not) swim in this river. Its water is heavily polluted.
g  We arrived here so late that we __________ take a taxi.
h  I know that you __________ stay at home helping your mother yesterday, but you could have phoned me6 to tell me you weren't coming.
i  We __________ leave at once, or else we'll get there late.
j  She __________ (not) have failed her exam. She studied very hard.
k  What they say __________ (not) be true. They __________ be wrong.
l  You __________ (not) park the car in the car park. I'll be using it this afternoon.
m  You __________ (not) have gone all that way on foot. You could have caught a bus!
n  I'm afraid to tell you that you __________ repeat the year. You've got the poorest marks in the class.
o  We __________ (not) make the beds. The maid will make them.
p  You __________ (not) drink and drive. It's a very dangerous combination.
q  She __________ (not) come to work yesterday, so she stayed at home.
r  I __________ take that train, otherwise I won't get there in time for the meeting.
s  She __________ pay us a visit the next time she comes to town. We insist on it.
t  You __________ take some exercise. You're putting on weight.
u  This plant __________ be watered every evening, or it'll wither.
v  We had an accident, so we __________ call a breakdown truck.
w  You __________ (not) ring up the police, or we'll be put away for theft.
x  You __________ slow down. Your health is very poor. Nevertheless, it is up to you.
y  You __________ (not) help us. We don't need any help.
z  We got a puncture and __________ change the wheel.


1  Do not need to es una alternativa a do not have to:
   You do not have to / do not need to wash that by hand. You can use the dishwasher. (No hace falta que laves eso a mano. Puedes usar el lavavajillas.)
2  En vez de must not, se puede usar cannot:
   You cannot eat all that. It's very spicy and hot. (No puedes comerte todo eso. Está muy condimentado y es muy picante.)
   You can't overtake. There is a continuous line here. (No puedes adelantar. Hay línea continua aquí.)
   Vea nuestra gramática de nivel avanzado para más informacion sobre must not y cannot.
3  En vez de should, se puede usar ought to: You ought to cut down your expenses. (Deberíais reducir los gastos.)
4  Aquellos con un nivel más avanzado tal vez quieran ver la diferencia entre need not have + participio de pasado y did not need to/did not have to.
5  Verbo modal + have + participio de pasado se refiere al pasado. Vea nuestra grámatica de nivel avanzado para más información.
6  You could have phoned me (= podrías haberme llamado por teléfono) indica reproche.
Autor: Miquel Molina i Diez
Pulse aquí para ver las soluciones


1.  El verbo "to be" (la clave)

2.  Los verbos modales "can" y "may" (la clave)

3.  El verbo "have" (la clave)

4.  Have to, must, need not, cannot y should (la clave)

5.  El presente simple y el presente continuo (o progresivo) (la clave)

6.  El pasado simple y el pasado continuo (o progresivo)

7.  El presente perfecto simple, el pasado simple, el presente perfecto continuo, el pasado perfecto simple y el pasado perfecto continuo

8.  La perífrasis "be going to", el presente continuo y el futuro simple

9.  Verbos irregulares

10.  Subordinadas condicionales

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