地层接触关系总体上分为()2种。
A、整合接触和平行不整合接触
B、平行不整合接触和角度不整合接触
C、整合接触和不整合接触
D、整合接触和角度不整合接触
参考答案:C
The boy is lying on the ground, _________ at the aeroplane in the sky.
A.looked
B. to look
C.look
D.looking
保密工作机构应当配备必要的保密()工具。