【正确答案】It is very necessary that a person do exercises every day, if he wishes to be healthy. /It is very necessary for a person to do exercises every day, if he wishes to be healthy.

【答案解析】此句考查的重点有两个：一是条件从句；二是考生对形式主语句式结构的掌握。此外，如果考生将实际主语译成从句形式，还要注意在“it is necessary that...”之后的从句中，不管主语是单数还是复数，动词都要用原形。