What is the output of this program?

#include<stdio.h>
#include<pthread.h>
 
int a;  
void *fun_t(void *arg);
void *fun_t(void *arg)
{       
    a = 20;
    pthread_exit("Bye");
}
int main()
{
    pthread_t pt;
    void *res_t;
    a = 10;        
    if(pthread_create(&pt,NULL,fun_t,NULL) != 0)
        perror("pthread_create");
    if(pthread_join(pt,&res_t) != 0)
        perror("pthread_join");
    printf("%d\n",a);
    return 0;
}

A. 10

B. 20

C. segmentation fault

D. none of the mentioned

Answer: Option B