1 . The first trial of this medicine took place in 1899, _______ the company, _______ Hoffmann worked, began distributing（分发；分配） the medicine in powder（粉末） form to physicians to use with patients.

A．when; which

B．when ; for which

C．which; in which

D．which; where

2 . We will put off the picnic in the park until next week, ________ the weather may be better.

A．that	B．where
C．which	D．when

3 . Great changes have taken place in that school. It is no longer ___ it was 20 years ago, ___ it was so poorly equipped.

A．what, when

B．that, which

C．what, which

D．which, that