the internet is I do not think it is a good idea to spend too much time on it.A. When ;

问题补充：

the internet is , I do not think it is a good idea to spend too much time on it.

A. When ; helpful

B. As ; great help

C. While ; of great help

D. Now ; of no help

答案：

A. When ; helpful

B. As ; great help

(答案→)C. While ; of great help

D. Now ; of no help

解析：考查连词。句中while作“虽然”之意；be of great help = very helpful。句意：虽然网络是很有帮助的，但我认为在它上面花太多的时间不是一个好主意。