So far no life has been found outside the earth, but while some scientists are actively searching for living things in outer space, others firmly believe there ____ .

A. mustn’t be                B. may not be               C. can’t be             D. won’t be

So far no life has been found outside the earth, but while some scientists are actively searching for living things in outer space, others firmly believe there ______.

So far no life has been found outside the earth, but while some scientists are actively searching for living things in outer space, others firmly believe there ____ .

A. mustn’t be 　　 B. may not be

C. can’t be 　　　　　 D. won’t be

So far no life has been found outside the earth, but while some scientists are actively searching for living things in outer space, others firmly believe there ____ .

A. mustn’t be 　　 B. may not be

C. can’t be 　　　　　 D. won’t be

So far no life has been found outside the earth, but while some scientists are actively searching for living things in outer space, others firmly believe there ______.

1. A.
   mustn’t be
2. B.
   may not be
3. C.
   can’t be
4. D.
   won’t be