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

• int xstrlen(char *s) { int length=0; while(*s!='\0') { length++; s++; } return (length); }
• int xstrlen(char s) { int length=0; while(*s!='\0') length++; s++; return (length); }
• int xstrlen(char *s) { int length=0; while(*s!='\0') length++; return (length); }
• int xstrlen(char *s) { int length=0; while(*s!='\0') s++; return (length); }

#include<stdio.h>

int xstrlen(char *s)
{
    int length=0;
    while(*s!='\0')
    { length++; s++; }
    return (length);
}

int main()
{
    char d[] = "CuriousTab";
    printf("Length = %d\n", xstrlen(d));
    return 0;
}