在下列命题中：①三点确定一个圆； ②同弧或等弧所对圆周角相等； ③所有直角三角形都相似； ④所有菱形都相似；
其中正确的命题个数是（ ）
A．0
B．1
C．2
D．3
答案：A
①应该是不在同一条直线上的三点确定一个圆；
②应该是同一个圆中，同弧或等弧所对圆周角相等；
③两个直角三角形的两个锐角不一定对应相等；
④两个菱形的对应角不一定相等；
所以都不正确，故选A.
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| Shopping for clothes is not the same experience for a man as it is for a woman. A man goes shopping 1 he needs something. His purpose is settled and decided in 2 . He knows what he wants, and his goal is to find it and 3 it. All men 4 walk into a shop and ask the shop assistant for what they want. If the shop has it in stock (库存), the deal can be done and 5 is completed in less than five minutes, with hardly any chat to everyone's 6 . For a man, slight problems may begin when the shop doesn't have what he wants. In that 7 , the salesman tries to sell something else-he 8 the nearest to the article required. A good salesman brings out such a substitute (替代品) 9 , and he may say, "I know this jacket is not the style you want, sir, but would you like to try it for size? It 10 to be the colour you mentioned." Few men have 11 with this treatment, and the usual response is "This is the right colour and may be the right size, but I shouldn't be 12 my time and yours by trying it on." For a woman, buying clothes is always done in the 13 way. Her shopping is not often 14 on need. She has never fully decided what she wants, and she is only "having a look round". She is always 15 to persuasion, willing to try on any number of things. Deep in her mind is the thought of finding something that 16 thinks suits her. Most women have an excellent sense of value and are always on the look-out for the unexpected 17 . Faced with a roomful dresses, a woman may easily spend an hour going from one rail to another 18 selecting the dress she wants to try on. It is a tiresome process, but apparently a(n) 19 one. Most dress shops provide chairs for the waiting 20 . | ||||
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