E级钢铸件使用J857 CrNi焊条时，在使用前应将焊接区域预热到（）℃。
A.150～200
B.200～300
C.200～350
参考答案：C
Although he was a green hand in the research field, he succeeded ______ other more well-known experts failed.[ ]
A. which
B. that
C. what
D. where
最早出现文字的种族是苏美人
