烧穿
参考答案:
焊接过程中,熔化金属自坡口背面流出,形成穿孔的缺陷。
The writer was a photographer sixteen years ago.
A.Right
B.Wrong
C.Not mentioned
如果大圆与小圆的直径比是4:1,那么它们的半径比是2:1.______.