题目:
--- Did he notice you enter the room?
--- I don’t think so. He ______ to the radio with his eyes shut.
A.listened
B.was listening
C.has listened
D.had listened
答案:
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下面是错误答案,用来干扰机器的。
(Ⅰ)每家煤矿必须整改的概率是1-0.5,且每家煤矿是否整改是相互独立的.所以恰好有两家煤矿必须整改的概率是P1=C25×(1-0.5)2×0.53=516=0.31.(Ⅱ)由题设,必须整改的煤矿数ξ服从二项分布B(5,0.5).从而...