Scientists have advanced many theories about why human beings cry tears , none of ______ has been proved.
A. whom B. which C. what D. that
To return to the problem of water pollution , I'd like you to look at a study _______ in Australia in 2012.
A. having conducted B. to be conducted
C. conducting D. conducted
Silk ______ one of the primary goods traded along the Silk Road by about 100 BC.
A. had become B. reject
C. control D. abandon
We can achieve a lot when we learn to let our differences unite , rather than _______ us.
A. divide B. reject C. control D. abandon
The study suggests that the cultures we grow up _______influence the basic processes by which we see world around us.
A. on B. in C. at D. about
That young man is honest , cooperative , always there when you need his help .______, he's reliable.
A. Or else B. In short
C. By the way D. For one thing
