Gramática inglesa de nivel medio paso a paso (Intermediate English Grammar Step by Step)
Observe que puede haber otras opciones a las respuestas dadas. Además, se ha usado / para indicar alternativas diferentes.
a can't / cannot, be able to b could c Can, could, can't / cannot d be able to e been able to
a could b was able to c could not / couldn't d could e was able to
a Can / May / Could b can / may c been allowed to d could e Can
a may b may c can d may not e Do you think (that)
a may / might, may / might, can't / couldn't b could c can't / couldn't d can't / couldn't e could
a Can, can't b was able to c may / could / might d could e can f may g can't h Do you think (that) i can't j can, can't k Can / May / Could, can / may l could m be able to n May / Could o be able to p could / might q been able to r may / could / might s may / could / might t can / may u May v may w could, can't x can't y can't z could