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 1st one gets 20 points totally, the 2nd one gets 10, the 3rd one gets 9 and the 2nd one picks number c at the last round, then who picks number b at the first round?
A. The 1st one
B. The 2nd one
C. The 3rd one
D. Can't be found out