用计数器测得某放射性物质半小时内发出的脉冲数为390个,该放射性物质每10分钟内平均发出脉冲数的95%可信区间为()
A.
B.
C.
D.
E.
参考答案:C
William, as well as his friends,________invited to my birthday party the day before yesterday.
A.is
B.was
C.are
D.were
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