What is the output of the following code?

#include<stdio.h>
#include<string.h>
int max_num(int a, int b)
{
      if(a > b)
         return a;
      return b;
}
int lcs(char *str1, char *str2)
{
      int i,j,len1,len2;
      len1 = strlen(str1);
      len2 = strlen(str2);
      int arr[len1 + 1][len2 + 1];
      for(i = 0; i <= len1; i++)
          arr[i][0] = 0;
      for(i = 0; i <= len2; i++)
          arr[0][i] = 0;
      for(i = 1; i <= len1; i++)
      {
          for(j = 1; j <= len2; j++)
          {
              if(str1[i-1] == str2[j - 1])
                  arr[i][j] = 1 + arr[i - 1][j - 1];
              else
                  arr[i][j] = max_num(arr[i - 1][j], arr[i][j - 1]);
          }
      }
      return arr[len1][len2];
}
int main()
{
      char str1[] = "hbcfgmnapq", str2[] = "cbhgrsfnmq";
      int ans = lcs(str1,str2);
      printf("%d",ans);
      return 0;
}

A. 3

B. 4

C. 5

D. 6

Answer: Option B