用所给单词的适当形式填空。

1. Mary told me that she had been to China ____ (two).

2. Here are the results of the _____ (student) activity survey at Hilltop High School.

3. Can you tell me who is the _____ (healthy) student in your class?

4. My _____ (eat) habits are pretty good.

滑石的化学通式为：（）。

A、BaCO3·MgCO3

B、BaCO3·Al2O3

C、3MgO·4SiO2·H2O

D、Al2O3·10H2O