问题

____ volcanoes now for many years, I am stillamazed at their beauty as well as their potential to cause great damage.

A:Studied
B:To study
C:Havingstudied
D:Studying

正确答案是：

同类题型

has previous experience, ______ I think he’s the right person for the job.

Please call Alan_____2722231.

Our teacher always speaks slowly and clearly in class ______.

The children are laughing _____.They look_______.

. Whoever has_____sense knows smoking is harmful to people’s health