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【单选题】
In the late 1990s the Quebec government launched a massive geologic expedition to make the first detailed maps of the northern reaches of the province.A.
the distance to which someone can stretch out their hand
B.
the extent or range of application, effect, or influence
C.
a continuous extent of land or water, especially a stretch of river between two bends, or the part of a canal between locks
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举一反三
【单选题】若随机变量 的数学期望与方差都存在,对 a
A.
P(a
B.
P(a
C.
P(-a
D.
P( b-a)
【单选题】若随机变量X的数学期望与方差都存在，对a
A.
P(a
B.
P(-a
C.
P(X
D.
P(|X-E(X)|
【单选题】若随机变量X与Y数学期望和方差都存在，且已知E(XY)=E(X)E(Y), 则下列正确的是（ ）
A.
D(X+Y)=D(X-Y)
B.
X与Y独立
C.
D(X)=D(Y)
D.
D(XY)=D(X)D(Y)