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【简答题】
随机变量X与Y相互独立，且D（X）=4，D（Y）=2，则D（3X－2Y）＝（）。
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举一反三
【单选题】学生害怕在社交场合讲话，担心自己会因发抖、脸红、声音发颤、口吃而暴露自己的焦虑，觉得自己说话不自然，因而不敢抬头，不敢正视对方眼睛。这种是( )心理症状。
A.
抑郁症
B.
恐怖症
C.
焦虑症
D.
神经质
【单选题】Grandpa Edwin was a soldier, a __________ Army officer who served in World War I.
A.
proceedings
B.
processing
C.
professional
D.
projecting
【单选题】Heavy food ( ) not ( )people who have just recovered from a stomach-ache.
A.
is…served with
B.
is…suited for
C.
is…famous for
D.
is adapted for
【单选题】I’d like to_______ that the staff member who served me didn’t really seem to know what he was doing.
A.
point out
B.
point at
C.
point in
【单选题】Who will be served in the meeting?
A.
salesmen
B.
the general manager
C.
VIP patrons
D.
telephone operators
【单选题】— Can I help you, madam? — No, thank you. I _____ now. [ ]
A.
have been served
B.
have served
C.
am being served
D.
am serving
【单选题】______, the author felt that she was working for those who she served.
A.
Since she worked in the bookstore after school
B.
When she could help people make sense of the world
C.
If she sensed she was working for the customers
D.
Though she worked for certain companies and got paid by them
【单选题】Another excellent mouse was Jerry, who served a London post office for ______ years.
A.
six
B.
sixteen
C.
twenty-four
D.
twenty
【单选题】Medical personnel who served in heavy combat in a recent war—even those who escaped physical injury—now have lower incomes and higher divorce rates, and score lower on psy chological profiles measurin...
A.
The medical personnel who served in heavy combat had completed significantly less schooling prior to military service than had other medical personnel.
B.
The medical personnel who served in heavy combat tended to be younger at the time of their entry into military service than were other medical personnel.
C.
Parents of medical personnel who served in heavy combat show no significant difference in incomes, divorce rates, or general happiness from parents of other medical personnel.
D.
Income levels, divorce rates, and levels of general happiness are the same for the medical personnel who served in heavy combat as they are for construction workers.
E.
Medical personnel who served in heavy combat in an earlier war show no significant difference in incomes, divorce rates, or general happiness from other medical personnel who served in that war.
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