碱性焊条在大电流范围内焊接时可发生（）
A、大滴状过渡
B、细滴状过渡
C、短路过渡
D、渣壁过渡
参考答案：A, C
Tim's mum is worried _____ her son's eyesight as he plays online games too much. [ ]
A. for
B. about
C. with
D. of
TS16949：2009是由什么共同制定的？
