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【多选题】
单选 若函数y=f(x)在点x=x0处取得极大值，则必有（）
A.
f′(x0)=0
B.
f″(x0)�0
C.
f′(x0)=0,f″(x0)�0
D.
f′(x0)=0或x0处导数不存在
参考答案：
参考解析：
刷刷题刷刷变学霸
举一反三
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【单选题】What is the main aim of book review? （单选）
A.
analyzing a perspective or argues a point
B.
analyzing or discussing researches previously published by others
C.
summaries and comments on a newly published academic book
D.
summaries, reviews and comments the research trends, the major discoveries, significant findings, the leading opinions on a particular subject.