#include<bits/stdc++.h>
using namespace std;
#define MAXN 200005

int n;
int fa[MAXN];
vector<int> to[MAXN];

vector<pair<int, int>> ans;
int find(int x) {return fa[x] == x ? x : fa[x] = find(fa[x]);}
void merge(int x, int y) {
    ans.push_back({x, y});
    int fx = find(x), fy = find(y);
    fa[fx] = fa[fy] = min(fx, fy);
}

void work() {
    cin>>n;
    for(int i=1;i<=n;i++) fa[i] = i;
    for(int i=1;i<=n;i++) {
        int k, x; cin>>k;
        for(int j=1;j<=k;j++) cin>>x, to[x].push_back(i);
    }
    
    for(int i=n;i>=1;i--) {
        if(!to[i].size()) continue;
        sort(to[i].begin(), to[i].end());
        for(int j=0;j+1<to[i].size();j++) {
            merge(to[i][j], to[i][j+1]);
        }
        merge(to[i].back(), find(i));
    }

    for(auto [x, y] : ans) printf("%d %d\n", x, y);

}
void clear() {
    for(int i=1;i<=n;i++) to[i].clear();
    ans.clear();
}

int main() {
    ios::sync_with_stdio(false), cin.tie(0);
    int t;
    cin>>t;
    while(t--) work(), clear();
    return 0;
}