EGW表示为（）。A、等离子弧焊 B、气电立焊 C、脉冲熔化极焊 D、螺柱焊接

There was nothing to do but _____ till mother came back. [ ]

A. waited

B. waiting

C. to wait

D. wait

Last night Tom dropped in________my home and______some books.[ ]

A．on; asked for  

B．at; asked for

C．to; asked  

D．∕； wanted

输卵管妊娠应立即手术治疗的是

A． * * 持续出血
B．休克
C．后穹隆穿刺抽出血液
D． * * 娠试验阳性
E．一侧附件扪及包块

补充新的SF₆气体前，钢瓶内SF₆气体微水含量不超过（）

A.150ppm

B.15ppm

C.68ppm