7. (10 points) Two people, A and B, play the following game. They first agree on an integer $N$, then A starts, and they take turns filling in one of the digits 1, 2, 3, 4, 5, 6, 7, 8, 9 in any of the following squares: $\square \square \square \square \square \square$. Each square is filled with only one digit, forming a six-digit number that can have repeated digits. If this six-digit number is divisible by $N$, B wins; otherwise, A wins. When $N$ is less than 15, the $N$ that ensures B has a winning strategy is ( )
A. 5
B. 6
C. 7
D. 8
【Solution】Solution: If $N$ is even, player A only needs to fill in an odd number in the unit place for the first time, and player B will definitely lose. Therefore, we only need to consider the case when $N$ is odd. When $N=1$, it is obvious that player B will definitely win.
When $N=3,9$, player B only needs to match the digit sums $1-8,2-7,3-6,4-5,9-9$.
When $N=5$, player A fills in a number that is not 5 in the unit place, and player B will definitely lose.
When $N=7,11,13$, player B only needs to form $\overline{\mathrm{abcabc}}=\overline{\mathrm{abc}} \times 1001=\overline{\mathrm{abc}} \times 7 \times 11 \times 13$, hence the answer is: B.