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

using i64 = long long;

int main() {
    cin.tie(nullptr)->sync_with_stdio(false);

    int t;
    cin >> t;

    auto solve = [&]() {
        int n, m;
        cin >> n >> m;

        vector<vector<int>> adj(n);
        for (int i = 0; i < m; i++) {
            int u, v;
            cin >> u >> v;
            u--, v--;
            adj[u].push_back(v);
            adj[v].push_back(u);
        }

        vector<int> vis(n), dep(n);
        int sq = 0;
        while (sq * sq < n) {
            sq++;
        }
        vector<vector<int>> verts(sq);

        auto dfs = [&](auto dfs, int u) -> void {
            verts[dep[u] % sq].push_back(u);
            vis[u] = true;
            for (auto v : adj[u]) {
                if (!vis[v]) {
                    dep[v] = dep[u] + 1;
                    dfs(dfs, v);
                }
            }
        };
        dfs(dfs, 0);

        int x = 0;
        for (int i = 0; i < sq; i++) {
            if (!verts[i].empty() && verts[i].size() < verts[x].size()) {
                x = i;
            }
        }

        cout << verts[x].size() << '\n';
        for (auto u : verts[x]) {
            cout << u + 1 << " \n"[u == verts[x].back()];
        }
    };

    while (t--) {
        solve();
    }
    
    return 0;
}