400-1816-180
本題由chris提供
A gardener is going to plant 2 red rosebushes
A.1/12
B.1/6
C.1/5
D.1/3
E.1/2
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答案：
B
C(2，1)C(2，1
)/A(4，4)
隨機挑花排序所以是A(4，4),
然后它說中間兩個位置是紅花的概率。
假設(shè)四個位置分別為1、2、3、4.
種第1個位置時，只能種白花，白花有2朵，所以是2選1，C(2,1)=2
種第2個位置時，只能種紅花，那么只有在2朵紅花里面選一朵來種，也是2選1，C(2,1)=2
種第3個位置時，只有1朵紅花可以選了，所以是C(1,1)=1
種第4個位置時，因為也只剩一朵花了，也是C(1,1)=1
所以中間是紅花的的選法有2x2x1x1=4
所以4/24=1/6，選B。 
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