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问题
单项选择题
用防错装接头进行充装时，防错装接头零部件是否（）。
A、磨损
B、灵活好用
C、完好
答案
参考答案：
B
选择题
— He didn't devote his time
to his study, did he?
— _____. As a result, he failed all the final exams.
A. Yes, he did
B. No, he didn't
C. Yes, he didn't
D. No, he did
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问答题
设随机变量X服从参数为λ的指数分布，令
求：
1.P{X+Y=0}；
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