--- I saw the Smiths at West Beijing Station this afternoon.

--- You __________. They are still on holiday in Hawaii.

A. mustn't have       B. shouldn't           C. couldn't have       D. needn't

--- I saw the Smiths at West Beijing Station this afternoon.
--- You ______. They are still on holiday in Hawaii.

1. A.
   mustn't have
2. B.
   shouldn't
3. C.
   couldn't have
4. D.
   needn't