十字作业的内容是()、润滑、紧固、调整、防腐。
A.清洁
B.除锈
C.清洗
D.除尘
参考答案:A
He once worked in a company, _____ he went abroad for further study.
A.from which
B.after that
C.after which
D.from this
简述可行性研究报告包括的主要内容。