The library function used to find the last occurrence of a character in a string

The library function used to find the last occurrence of a character in a string is

2) What will be the output of the following program?

void main()
 {
       char str1[] = "abcd";
       char str2[] = "abcd";
       if(str1==str2)
             printf("Equal");
       else
             printf("Unequal");
 }

3) What is the output of this C code?

#include <stdio.h>
     int main()
     {
         char str[11] = "hello";
         char *str1 = "world";
         strcat(str, str1);
         printf("%s %d", str, str[10]);
     }

4) Which is more appropriate for reading in multi-word string?

5) What is the output of this C code?

#include <stdio.h>
     int main()
     {
         char *str = "hello, world";
         char *str1 = "hello, world";
         if (strcmp(str, str1))
             printf("equal");
         else
             printf("unequal");
     }