电动液压锚机的特点是：（）
①、操作平稳；②、变速性能好；③、制造技术和维护保养要求高
A.①、②、③
B.①、②
C.②、③
D.①、③
参考答案：A
- The book on the desk is Tom's, isn't it?
- No, it's _____. [ ]
A. someone else
B. someone else's
C. else someone's
D. else someone
凡航行前往其它缔约国所辖港口的船舶，应持有由主管机关签发的IOPP证书，其有效期不超过（）年。
A.1
B.2
C.4
D.5
