刨削加工与水平方向成60°角的斜面时,刀架应转动()
A.90°
B.60°
C.30°
D.任意角度
参考答案:C
Tens of thousands of trees _____ in the area in the past few years.
A.have been planted
B.were planted
C.have planted
D.had planted
一般所谓的地震资料应包括地震剖面、底图、各种速度资料,各种()成果及从野外获得的资料等。