下列不属于钢管无损探伤的外观缺陷的是（）。
A、咬边
B、焊瘤
C、凹陷
D、成形不良
参考答案：D
Without friendship, one can't be happy although he is rich enough.
As for me, I will never forget the days _____ I spent with my dearest friend.[ ]
A. that
B. when
C. who
简述杉木营造技术措施？
