[求助]蓝皮书数学DS题第78题求解？

lujibo

78. Bowls X and Y each contained exactly 2 jelly beans, each of which was either red or black. One of the jelly beans in bowl X was exchanged with one of the jelly beans in bowl Y. After the exchange, were both of the jelly beans in bowl X black?

(1)Before the exchange, bowl X contained 2 black jelly beans.

(2)After the exchange, bowl Y contained 1 jelly bean of each color.

我觉的答案应该是D，可是参考答案是E。主要是我没有理解each of which was either red or black是什么意思，求高手解答。多谢

waterk

应该是E
X: BB
Y: WB 和 WW都有可能WB的结果

[此贴子已经被作者于2009-6-2 23:48:11编辑过]

lujibo

each of which was either red or black是什么意思，是不是说每个盘子里都各有一个白球、一个黑球