问题
单项选择题
安全阀处于关闭状态，密封面间无介质泄漏时的压力叫做（）。
A.密封压力
B.开启压力
C.回座压力
答案
参考答案：A
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安全阀处于关闭状态，密封面间无介质泄漏时的压力叫做（）。
A.密封压力
B.开启压力
C.回座压力
参考答案：A
There is no doubt that the friends can improve our lives, kind of friend someone has. There are some good reasons why real are important. Real fiends can be a source(资源) of _ .When you are in trouble， for example， true friends will hope. Real fiends may help a friend to be as a student president，and the president of a country. Some of us will remember that school，work and life are better and more fun when with fiends. And there are other reasons why real friends are . You can quickly real and good fiends when you are down or when you need their help the most. Why? Because a real fiend will not you when you are down，and will not turn against you in jealousy(妒忌)，for example，when you succeed.
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