X射线机按（）分类可分为：便携式、固定式、移动式。

A.结构

B.大小

C.穿透能力

D.冷却方式

根据句意和首字母提示完成下列句子。

小题1:There are sixty m___________ in an hour．

小题2:He is ill, and his i__________ makes us feel sad．

小题3:A lot of t__________ are visiting the Great Wall, so it is very crowded．

小题4:Good food and e__________ help me to study better．

小题5:It is n_________to eat a balanced diet.