____ volcanoes now for many years, I am still amazed at their beauty as well as their potential to cause great damage.
#91442
A
Studied
B
To study
C
Having studied
D
Studying
推荐题目
He was sent to Australia _______ when he was ten years old.
#95654
A
to be educated
B
to educate
C
educating
D
to be educating
 The machine has been made easier for it____.
#94295
A
to operate
B
operated
C
being operated
D
to be operated