沟槽中心线每侧的净宽不应小于沟槽底部开挖宽度的（）。
A．1倍
B．1/2
C．2倍
D．1/3
参考答案：B
What did the person do during the vacation a. Stayed at home. b. Exhausted myself. c. Hardly had any rest. d. Don’t know.
祖母绿原石晶体是呈（）
A、三方柱
B、四方柱
C、六方柱
D、斜方柱
