Question

[Ai Ai]

There're three distinct whole numbers a,b,c displayed on three cards. In each round, each of three students picks one card randomly in turn then record their numbers. They play at least two rounds. If after the last round, the 1^st one gets 20 points totally, the 2^nd one gets 10, the 3^rd one gets 9 and the 2^nd one picks number c at the last round, then who picks number b at the first round?

A. The 1^st one

B. The 2^nd one

C. The 3^rd one

D. Can't be found out