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
I have never seen the word ______ that way before.
A. to use B. used C. using D. to be used
I appreciated ____ the opportunity to study abroad two years ago.
A. having been given B. having given
C. to have been given D. to be given
The International Day against Drugs, aimed at warning people to keep away from drugs， _________ on June 26th every year．
A.taking place B.takes place C.took place D.taken place
. Progress so far has been very good. _______, we are sure that the project will be completed on time.
A. However B. Otherwise C. Therefore D. Besides
Only when you leave your parents for college education _______ how much you love them.
A. do you realize B. you realize C. you will realize D. will you realize
