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【单选题】
设随机变量 的方差存在,则( ).A.
;
B.
;
C.
;
D.
.
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参考答案：
参考解析：
知识点：
皮皮学刷刷变学霸
举一反三
【单选题】What is the main purpose of the laptop computer program in Westlake College?
A.
To give the students more free time to do their school work.
B.
To give the students help in their homework out of classes.
C.
To offer the students more chances to work in the future.
D.
To allow the students to do school work anywhere.
【简答题】鲜的青蒿,用作药料
【单选题】下列药物，用法错误的是
A.
番泻叶，开水泡服，入煎剂宜后下
B.
穿心莲，煎服或作丸、散、片剂服用
C.
青蒿，煎汤或鲜用捣烂绞汁服
D.
紫草，煎服或作散剂，外用熬膏
E.
青黛，煎服
【单选题】The main purpose of announcing the above events is to give information about______.
A.
visiting teams
B.
famous players
C.
things to do for the weekend
D.
prices to pay for the sports events
【单选题】The main purpose of the passage is to ______.
A.
give a brief introduction to the growth of the mass newspaper
B.
trace the cause of the failures of the six-cent papers
C.
find out which was the most significant newspaper of that time
D.
show how a mass-appeal newspaper made a great fortune
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