Ants smell things . Let’s watch them when we are free. — That sounds .

It is in this laboratory ______ is run by Mr. Wu ______ the experiments are done.

It is generally believed that Watson and Crick’s discovery about DNA was ____ beginning of _____ enormous advances in _____ field of genetics.

Hardly could he______this amount of work in such a short time.

He is fluent in English because he once stayed in London —- Really ? How long _________ there ?