钻头到达井底后，将钻头上提（），同时循环钻井液。
A.0.1～0.2m
B.2～0.3m
C.0.3～0.5m
D.0.5～1m
参考答案：B
Tom had prepared carefully for his driving test so that he could be sure of passing it on his first .
A．attention
B．expectation
C．attempt
D．desire
为什么电容具有“通交流、隔直流”的特性？
