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一、选择题1.把2棵枫树、3棵橡树、4棵桦树随机地栽成一行,各种不同的安排顺序都是等可能的.那么,任何2棵桦树都不相邻的概率是().A.5/(21) B.5/(42) C.7/(99) D.9/(100)2.某人有5把钥匙,其中有2把是房门钥匙.但他忘记了开房门的是哪2把,只好逐一试开.那么,他在3次内打开房门的概率是().A.3/5 B.1/5 C.9/(10) D.7/(10)3.三个猎人同时向一只兔子射击,他们射中的概率分别是0.6,0.5,0.4.则三人同时向兔子射击一次,这只兔子被击中的概率是().A.0.88 B.0.12 C.0.85 D.0.15
First, the multiple-choice questions 1. The two maples, three oaks, four birch trees planted in a row, all sorts of different arrangements are possible. So, any two birch are not adjacent The probability is () A.5 / (21) B.5 / (42) C.7 / (99) D.9 / (100) 2. Someone has five keys, two of which are door keys But he forgot which two of the doors were opened and had to try it out one by one, so the probability that he would open the door within three (3) times was (A.3 / 5) B.1 / 5 C.9 / ( 10) D.7 / (10) 3. The three hunters shot at the same time to a rabbit, the probability of their shot were 0.6,0.5,0.4. The three shot at the same time to the rabbit, the rabbit was hit The probability is () .A.0.88 B.0.12 C.0.85 D.0.15