I often think how interesting ( )English is 用studying 还是TO study

I often think how interesting ( )English is 用studying 还是TO study
I often think how interesting ( )English is 用studying 还是TO study

I often think how interesting ( )English is 用studying 还是TO study
to study ,"how...to"

。。。我也不知道。。。无能为力。

应该是 to study