what's your idea about students'____ (use) mobile phones at school? 高手来!

what's your idea about students'____ (use) mobile phones at school? 高手来!
what's your idea about students'____ (use) mobile phones at school? 高手来!

what's your idea about students'____ (use) mobile phones at school? 高手来!
using .
显然,students'是所有格结构,后面应该跟名词性短语.而ing形式有名词性质,故填using

using
What's your idea about students' using mobile phones at school?

using
前面搭配短语 what about,其中about是介词，后面接动词形式是要用【动名词】。

祝你开心如意！

used 不会是高考呢吧？

填using
典型的用法，举例如下：
Mary's listening is good!