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【简答题】
设独立随机变量X 1 ，X 2 ，X 3 的数学期望分别为2，1，4，方差分别为9，20，12． (1)计算2X 1 +3X 2 +X 3 的数学期望与方差； (2)计算X 1 -2X 2 +5X 3 的数学期望与方差．
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【简答题】完形填空。 Every day after breakfast, my mother would go to read the paper and my father would wear that old apron(围裙). For the next hour __ 1 __ would do the dishes, singing songs. I thought it was strang...
【单选题】下列说法正解的是 ( ) 。
A.
elif 语句 可以单独使用。
B.
Python 中有 switch-case 多分支选择语句。
C.
Python 中的循环语句不能嵌套使用。
D.
每个 if 语句后面都要使用冒号。
【单选题】When asked by news reporters, the film star of stage and screen ________ that he would pay a visit to Europe next week.(2012· 山东岚山一中月考)
A.
identified
B.
proposed
C.
approved
D.
confirmed
【单选题】The shocking news made me realize ________ terrible problems we would face.(2011·北京)
A.
what
B.
how
C.
that
D.
why
【单选题】In the eighteenth century, writers ______ hours in coffee houses, discussing the news of the day.
A.
used to spending
B.
would be spending
C.
used to spend
D.
were used to spend
【单选题】In the eighteenth century, Writers ______ hours in coffee houses, discussing the news of the day.
A.
used to spending
B.
would be spending
C.
used to spend
D.
were used to spend
【单选题】下列说法正解的是 ( ) 。
A.
每个 if 语句后面都要使用冒号。
B.
Python 中的循环语句不能嵌套使用。
C.
Python 中有 switch-case 多分支选择语句。
D.
elif 语句 可以单独使用。
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