单项选择题
Connecting elements of a mooring system should be fabricated from（）.
A.cast iron B.forged steel C.stainless steel D.cast steel
单项选择题 Chain slings are suitable for heavy slender articles，such as（）.
单项选择题 Chafing gear（）.
单项选择题 Before welding in a tank that has carried petroleum products，the tank must be certified by （）.
