---Someone’s been here. Who ___ it be? It looks like Helen.---It ___ be Helen.She is ill in hospital.

Every solid object ______ reflect a sound，varying according to the size and nature of the object． 

— Lucy doesn’t mind lending you her dictionary. — She _______. I’ve already borrowed one. 

I would rather you ____ it.

— But for your timely warning, we _____ into great trouble.— Well, you know we’re friends.