钻杆的主要作用是传递扭矩，输送钻井液，联接及延长钻柱以到达不断加深井眼的目的。
参考答案：对
—Hi, Jack! When did you arrive in Berlin?
—Last weekend .I a different culture since then.
A．was experiencing
B．will be experiencing
C．have been experiencing
D．had been experiencing
胃癌血管性介入治疗的禁忌证有哪些（）
A.进展期胃癌
B.肠梗阻
C.肠坏死
D.恶病质
E.凝血机制障碍
