A2. On the playground, there were 17 girls and 12 boys. What is the minimum number of additional children that need to come to the playground so that all of them can be divided into 2 equal groups, with the same number of girls and boys in each group?
(A) 1
(B) 3
(C) 5
(D) 7
(E) 9
A2. If at some point the children on the playground can be divided into 2 equal groups, with $\mathrm{v}$ each group having $n$ boys and $n$ girls, then the total number of girls on the playground is $2n$, which is an even number and equal to the total number of boys on the playground. For the number of girls on the playground to be even and equal to the number of boys, at least 1 girl and at least 6 boys must come to the playground. Therefore, at least 7 more children should come to the playground.