On which system call, this program (process) waits until the server responds?

#include<stdio.h>
#include<netinet/in.h>
#include<sys/types.h>
#include<sys/socket.h>
 
int main()
{
    int fd_client,fd, len;
    struct sockaddr_in add_server;
    fd_client = socket(AF_INET,SOCK_STREAM,0);
    if (fd_client == -1){
        perror("fd_sock");
        exit(1);
}
add_server.sin_family = AF_INET;
add_server.sin_port = ntohs(4001);
add_server.sin_addr.s_addr = inet_addr("127.0.0.1");
len = sizeof(add_server);
fd  = connect(fd_client,(struct sockaddr*)&add_server,len);
if(fd == -1)
    perror("connect");
    write(fd,"Hello\n",6);
    return 0;
}

A. socket()

B. connect()

C. both socket() and connect()

D. none of the mentioned

Answer: Option A