用钨极氩弧焊焊接低碳钢时应采用（）。
A.交流焊机
B.直流反接
C.直流正接
D.无要求
参考答案：C
妊娠合并甲亢时的治疗应首选
A．他巴唑
B．丙基硫氧嘧啶
C．碳酸锂
D．昔萘洛尔
E．碘剂
We went to Canada to travel and my cousin ______ as our guide.
A．played
B．showed
C．acted
D．performed
