Pigeons have been used as messengers because ______.
A: they have a built-in compass
B: they can cover 500 miles in a single day
C: they have special ability to tell directions
D: they can find their way home
A: they have a built-in compass
B: they can cover 500 miles in a single day
C: they have special ability to tell directions
D: they can find their way home
举一反三
- Scientists have found out how pigeons find their way home but they keep it as asecret.
- A single Chinese character can have different meanings according to the tone used to pronounce it.
- He ____ Tokyo, for I saw him a short time ago. A: must have gone to B: mustn't have been to C: can't have gone to D: can't have been to
- The room is in a mess; it _____ cleaned. A: can’t have been B: shouldn’t have been C: mustn’t have been D: wouldn’t have been
- The room is in a terrible mess; it （）cleaned. A: can’t have been B: shouldn’t have been C: mustn’t have been D: will have been waiting