阅读下面程序，完成后面的判断题和单选题。判断题正确填 A，错误填 B。

#include <cstdio>
#include <cstring>
#include <algorithm>

char a[1005], b[1005];
int dp[1005][1005];

int main() {
    scanf("%s", a + 1);
    scanf("%s", b + 1);
    int n = strlen(a + 1);
    int m = strlen(b + 1);
    for (int i = 1; i <= n; ++i) {
        for (int j = 1; j <= m; ++j) {
            if (a[i] == b[j])
                dp[i][j] = dp[i - 1][j - 1] + 1;
            else
                dp[i][j] = (dp[i - 1][j] > dp[i][j - 1]) ? dp[i - 1][j] : dp[i][j - 1];
        }
    }
    printf("%d\n", dp[n][m]);
    return 0;
}