Which of the following function is used to find the first occurrence of a given

Which of the following function is used to find the first occurrence of a given string in another string?

2) 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]);
     }

3) 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");
 }

4) What will be the output of the program ?

 #include<stdio.h>
 int main()
 {
     int i;
     char a[] = "\0";
     if(printf("%s", a))
         printf("empty string\n");
     else
         printf("not empty string \n");
     return 0;
 }

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");
     }