______ volcanoes for many years, I am st
题型:选择题
问题:
______ volcanoes for many years, I am still amazed at their beauty as well as their potential
to cause great damage. [ ]
A. Studied
B. Having studied
C. Studying
D. To have been studied
______ volcanoes for many years, I am still amazed at their beauty as well as their potential
to cause great damage. [ ]
A. Studied
B. Having studied
C. Studying
D. To have been studied