单项选择题
A.reduces and prevents corrosion of standing rigging
B.prevents corrosion of running rigging
C.reduces and prevents wear caused by the rubbing of one object against another
D.protects the body against extreme cold
单项选择题 Before welding in a tank that has carried petroleum products，the tank must be certified by （）.
单项选择题 Before welding can be done in a tank that has carried petroleum products，a certificate must be obtained from（）.
单项选择题 At the same time，it is（）for you to signify your acknowledgement of the responsibility for the collision by signing the copies of this letter hereto attached and to return me two copies in due time.