【单选题】According to the author, swans in captivity are______.
A.
happy unless their wings have been cut
B.
happy most of the time, but unhappy sometimes
C.
unhappy most of the time
D.
only happy when they are bringing up families
【单选题】脾有升清的功能,所谓 “ 升清 ”比较准确的 是指( )
【判断题】制冷剂在充灌前必须经过干燥脱水处理后方科使用。
【判断题】冷剂在充灌前必须经过干燥脱水处理后方科使用。