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Six ellipses are arranged length wise horizontally in 2 rows with 3 ellipses in each row. Two arrows pointing to the right diverge from a point labeled A on the left, passes through the center of the 2 sets of ellipses, and converge to a point labeled B on the right. The circumferences of the ellipses have arrowheads pointing in the clockwise direction above the center and in the counterclockwise direction below the center.

The map above shows the trails through a wilderness area. If travel is in the direction of the arrows, how many routes along the marked trails are possible from point A to point B ?

答案:C
问题:请问May老师,这道题要怎么做呀?谢谢! 查看答疑

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