对于焊缝表面缺陷的检测，应优先采用（）。
A、X射线探伤
B、超声波探伤
C、磁粉探伤
D、渗透探伤
参考答案：C
He doesn't do his homework _____. So he always makes some mistakes. [ ]
A. careful enough
B. enough careful
C. carefully enough
D. enough carefully
“角平分线上的点到角的两边的距离相等”的逆定理是（ ）。
