Which of the following function is correct that finds the length of a string?

Declaration: strcmp(const char *s1, const char*s2);

The strcmp return an int value that is

if s1 < s2 returns a value < 0

if s1 == s2 returns 0

if s1 > s2 returns a value > 0

Declaration:

char *strnset(char *s, int ch, size_t n); Sets the first n characters of s to ch

#include <stdio.h>
#include <string.h>

int main(void)
{
   char *string = "abcdefghijklmnopqrstuvwxyz";
   char letter = 'x';

   printf("string before strnset: %s\n", string);
   strnset(string, letter, 13);
   printf("string after  strnset: %s\n", string);

   return 0;
}

Output:

string before strnset: abcdefghijklmnopqrstuvwxyz

string after strnset: xxxxxxxxxxxxxnopqrstuvwxyz

Declaration: char *strrchr(const char *s, int c);

It scans a string s in the reverse direction, looking for a specific character c.

Example:

#include <string.h>
#include <stdio.h>

int main(void)
{
   char text[] = "I learn through CuriousTab.com";
   char *ptr, c = 'i';

   ptr = strrchr(text, c);
   if (ptr)
      printf("The position of '%c' is: %d\n", c, ptr-text);
   else
      printf("The character was not found\n");
   return 0;
}

Output:

The position of 'i' is: 19

The statement printf("\\n"); prints '\n' on the screen.

The function strstr() Finds the first occurrence of a substring in another string

Declaration: char *strstr(const char *s1, const char *s2);

Return Value:
On success, strstr returns a pointer to the element in s1 where s2 begins (points to s2 in s1).
On error (if s2 does not occur in s1), strstr returns null.

Example:

#include <stdio.h>
#include <string.h>

int main(void)
{
   char *str1 = "CuriousTab", *str2 = "ia", *ptr;

   ptr = strstr(str1, str2);
   printf("The substring is: %s\n", ptr);
   return 0;
}

Output: The substring is: iaCURIOUSTAB

gets(); collects a string of characters terminated by a new line from the standard input stream stdin

#include <stdio.h>

int main(void)
{
   char string[80];

   printf("Enter a string:");
   gets(string);
   printf("The string input was: %s\n", string);
   return 0;
}

Output:

Enter a string: CuriousTab

The string input was: CuriousTab

To scan a float value, %f is used as format specifier.

To scan a double value, %lf is used as format specifier.

Therefore, the answer is scanf("%f %lf", &a, &b);

Because, In fgets() we can specify the size of the buffer into which the string supplied will be stored.

To print a float value, %f is used as format specifier.

To print a double value, %lf is used as format specifier.

Therefore, the answer is printf("%f %lf", a, b);

Declaration: char *fgets(char *s, int n, FILE *stream);

fgets reads characters from stream into the string s. It stops when it reads either n - 1 characters or a newline character, whichever comes first.

Therefore, the string str contain "I am a boy\n\0"