弧坑仅是焊道末端产生的凹陷，是一种没有危害的缺陷。( )
参考答案：错
吸上线常用（）的扁钢制成。
A.50mm×8mm
B.80mm×5mm
C.50mm×4mm
D.40mm×5mm
The loading, unloading, transshipment and transit of inward and outward mail bags are （） Customs control and a covering way bill should be submitted to the Customs by the enterprise providing postal service.
A. subject to
B. upon
C. into
D. with
