I often ______ my new friends with their study.[ ]
A. help
B. see
C. join
答案：A
______ 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
对损伤修复的不利因素有（）
A.感染
B.低蛋白血症
C.服用消炎痛
D.糖尿病
E.肝硬化
