#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */  
    int q,a,b,c,d,i,n,arr[100],count;
    cin>>q;
    while(n--)
        {
    int n;
    cin>>n;
    for(int i=0;i<n*2;i++)
        {
        cin>>arr[i];
    }
    for(int i=0;i<n;i+=2);
        {   
            a=arr[i];
            b=arr[i+1];
             for(int j=i+2;j<i+4;j+=2)
               {
                  c=arr[j];
                  d=arr[j+1];
               }
           if(b==c && a==d)
               {
               count=count+2;
           }
            else if(b==c||a==d)
                {
                count++;
        }
            
       }
      if( count==n)
                {
                cout<<"YES"<<endl;
            }
        else
            {
            cout<<"NO"<<endl;
        }  
    }       
    return 0;
}