选词填空（can't have been\must be\must have been\can't be \may have been\may be)
He was in hospital yesterday.He___ill.
She has eaten a lot of meat at lunch.She____very tired.
He has eaten a lot of meat at lunch.He___seriously ill.
Bob___to Tokyo.He knows nothing about the place at all.
Where is Harry?He___in his room.I'm not sure.
Why was he late?He___busy.I'm not sure.