import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        int q=sc.nextInt();
        for(int i=0;i<q;i++){
            int flag=0;
            int n=sc.nextInt();
            int[] ar1=new int[2];
            int[] ar2=new int[2];
            for(int j=0;j<n;j++){
                if(j<2){
                    int x=sc.nextInt();
                    if(x<0)
                        x=x*-1;
                    int y=sc.nextInt();
                    if(y<0)
                        y=y*-1;
                ar1[j]=x;
                ar2[j]=y;
               
                }
                else{
                    int x=sc.nextInt();
                    if(x<0)
                        x=x*-1;
                    int y=sc.nextInt();
                    if(y<0)
                        y=y*-1;
                    if((x==ar1[0] || x==ar1[1] || x==ar2[0] || x==ar2[1] )&& (y==ar2[0]|| y==ar2[1]))
                    continue;
                    else{
                        flag=1;
                        break;
                    }
                }
            }
            if(flag==0)
                System.out.println("YES");
            else
                System.out.println("NO");
        }
    }
}