1. [单选题]A segregated ballast system is a system where
A. all ballast is processed through the oily water separator
B. ballast is taken on and discharged through a separate main deck
C. ballast and cargo tanks are separated by cofferdams
D. all ballast lines, tanks, and pumps are independent of those used for oil
2. [单选题]适任证书被吊销_____年后，才可向原签发机关申请较低等级或职务的适任证书。
A. 1
B. 2
C. 3
D. 4
