It was a pity that the great scientist died      his research unfinished. 

 --What do you think made Celia so happy?--______ a prize in the recent competition.

With the entrance examination _____ up, our classmates work harder and harder.

So far all cloned animals have suffered from some different serious disorders, ______ dying soon after birth.

With efforts _______ conservation, we may believe that people enjoy a healthy life without the environment around them ________.