Have you known DrJackson for a long time?—Yes, since she________ the Chinese Society

The blue hat is 10 yuan, and the black hat is ______ 10 yuan.

We often take part in after class activities（活动）. I like to play ____ basketball , but my brother likes to play ____ guitar .

We haven’t settled the question of __________it is necessary for him to study abroad.

These articles are written in simple language, _____makes it easy to read.