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

const int N = 1e5 + 1;

int t, n, m;
bool is_store[N];
vector<int> adj[N];

void input() {
    cin >> n >> m;
    for (int i = 1; i <= n; ++i) {
        is_store[i] = false;
        adj[i].clear();
    }
    for (int i = 0; i < m; ++i) {
        int u, v;
        cin >> u >> v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }
}

void solve() {
    int store = 0;
    for (int i = 1; i <= n; ++i) {
        int cnt = 0, total = 0;
        for (int v : adj[i]) {
            if (v < i) {
                cnt += is_store[v];
                total++;
            }
        }
        if (2 * cnt < total) {
            is_store[i] = true;
            store++;
        }
    }
    cout << store << "\n";
    for (int i = 1; i <= n; ++i) {
        if (is_store[i]) cout << i << " ";
    }
    cout << "\n";
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cin >> t;
    while (t--) {
        input();
        solve();
    }
}