Which of the following function sets first n characters of a string to a given c

Which of the following function sets first n characters of a string to a given character?

2) How will you print \n on the screen?

3) What will be the output of the program ?

 #include<stdio.h>
 #include<string.h>
 int main()
 {
     char str[] = "Study 2 Online\0 C Language MCQ\0";
     printf("%s\n", str);
     return 0;
 }

4) If the two strings are identical, then strcmp() function returns

5) 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]);
     }