求助NN解释怎么计算滴阿

A certain roller coaster has 3 cars, and a passenger is equally likely to ride in any 1 of the 3 cars each time that passenger rides the roller coaster.  If a certain passenger is to ride the roller coaster 3 times, what is the probability that the passenger will ride in each of the 3 cars?

A.        0

B.        1/9

C.        2/9

D.       1/3

E.        1

应该是2/9吧, 3*2/(3*3*3)

3*3*3是全部的可能值，3*2*1是这个人ride in each of the 3 cars的可能值

trust your explan. absolutely

thx