妈妈今年a岁，爸爸今年（a+2）岁，再过2年，他们相差的岁数是请选择CBA)l'f2c1e'V:b5_2t'g,l7c8T6U.M6P(G
A.42t'g,l7c8T6U.M6P(G
B.22t'g,l7c8T6U.M6P(G
C.a2t'g,l7c8T6U.M6P(G