进行气体保护焊时，正向焊接时熔深较小且焊缝较平。
参考答案：对
(大连市高三双基测试卷) If it were not for literature, the well-known writer J.K. Rowling _______ nowhere in life.
A．could go
B．must go
C．would have gone
D．should have gone
高能电子束用于肿瘤的放射治疗，始于哪个年代初期（）
A.30
B.40
C.50
D.60
E.70
