What is the meaning of the following C code if output is 0?

#include<stdio.h>
#include<time.h>
int main()
{
    struct tm *local;
    time_t t;
    t=time(NULL);
    local=localtime(&t);
    printf("%d",local->tm_isdst);
    return 0;
}

A. strlen() B. strlength() C. stringlen() D. strsize()

A. To print formatted text to the standard output B. To read text from the standard input C. To open a file D. To close a file

A. math.h B. stdlib.h C. cmath.h D. algorithm.h

A. Compares two strings and returns an integer indicating their relationship B. Copies one string to another C. Concatenates two strings D. Searches for a substring