假如你的身体失去了占体重2％的水分，你的大脑功能和工作水平会开始下降。如果再失去占体重4%到7％的水分，你就会觉得头晕目眩。

Sentence No. 1 Courses for adult students may be vocational or recreational, that is, they may be related to a person’s job or taken purely for interest and pleasure.

Sentence No. 5 If you lost 2 percent of your body weight in water, your brain power and performance level may start to weaken. Another 4 to 7 percent may leave you feeling dizzy.