the Internet is of great help I don’t think it’s a good idea to spend too much time on it

问题补充：

the Internet is of great help, I don’t think it’s a good idea to spend too much time on it.

A. If

B. While

C. Because

D. As

答案：

A. If

(答案→)B. While

C. Because

D. As

解析：考查状语从句（从属连词的选用）题干前半句的含义是：网络有很大的帮助；后半句的含义是：我认为花太多的时间在上面没有好处。根据题干含义，显然需要一个表转折或让步的词，即while，尽管。而A是如果，表条件，C是因为，表原因，D是因为和像…，表原因和方式。