在套电动机轴承时,不允许用铁锤在轴承周围敲打,可采用特制的钢管套,钢套一端镶一个()后,再敲打套装轴承。
A.不锈钢圈;
B.铜圈;
C.木圈;
D.胶圈。
参考答案:B
用适当的单词完成对话。
Tony: 1 are you 2 for vacation, Sonja?
Sonja: I'm going to Xingjian 3 two weeks.
Tony: That 4 interesting! What are you doing there?
Sonja: I'm going 5 in the mountains.How 6 you, Tony?
Tony: I'm 7 my friend in Naming.
Sonja: 8 9 are you staying there?
Tony: Just for four days. I don't like going away too long.
Sonja: Well, have a 10 time.Show me your photos when you get back to school.
1._____ 2._____ 3._____ 4._____ 5._____
6._____ 7._____ 8._____ 9._____ 10._____
在两种不同介质的声界面上,决定声波反射量的因素是:①折射系数;②超声波频率;③声特性阻抗()
A.①②
B.①③
C.③
D.②③
E.①②③