1.Anyone who sings well can part in the() in our school.是填activity还是activities?为什么?

1.Anyone who sings well can part in the() in our school.是填activity还是activities?为什么?
2.He is ()to make money to support(赡养)his parents
A.old enough B.enough old C.young enough D.enough old选哪个?为什么?
3.你应该尝试多吃点儿水果 You should () () more fruit.