变电所电气装置的接地装置中潮湿的或有腐蚀性蒸汽的房间内，接地线离墙不应小于（）mm。
A.10
B.15
C.20
D.25
参考答案：A
阅读理解。
Alice is an English girl. She is a nice girl,and she is my good friend (朋友). My name's Helen. My father
is Alan. My mother is Kate. I love them. I like green very much. My pen is green. My ruler is green, too.
1. Alice is _____ .
A. a English boy
B. a English girl
C. an English boy
D. an English girl
2. Helen's mother is _____.
A. Alice
B. Kate
C. Alan
D. Rose
3. Helen likes
A. green
B. red
C. blue
D. orange
4. Alan is Helen's _____ .
A. friend
B. mother
C. father
D. sister
5. _____ is Helen's good friend.
A. Alan
C. Helen
D. Alice
按照库仑强度理论，岩石破坏时破裂面与最大主应力作用方向的夹角为( )。
A．45°-φ/2 B．45° C．45°+φ/2 D．60°
