#include <bits/stdc++.h>
using namespace std;
void bfs(long long root, list<long long> adj[], vector<long long> &level) {
  level[root] = 0;
  queue<long long> qu;
  qu.push(root);
  while (!qu.empty()) {
    long long cur = qu.front();
    qu.pop();
    for (auto it : adj[cur]) {
      if (level[it] == -1) {
        level[it] = level[cur] + 1;
        qu.push(it);
      }
    }
  }
}
void solve() {
  long long V, E, a, b;
  cin >> V >> E;
  list<long long> adj[V + 1];
  vector<long long> level(V + 1, -1);
  for (long long i = 0; i < E; i++) {
    cin >> a >> b;
    adj[a].push_back(b);
    adj[b].push_back(a);
  }
  bfs(1, adj, level);
  map<long long, vector<long long> > mp;
  for (int i = 1; i <= V; i++) {
    mp[level[i]].push_back(i);
  }
  a = mp.size();
  vector<long long> ans1, ans2;
  for (int i = 0; i < a; i += 2) {
    vector<long long> hold = mp[i];
    for (auto it : hold) ans1.push_back(it);
  }
  for (int i = 1; i < a; i += 2) {
    vector<long long> hold = mp[i];
    for (auto it : hold) ans2.push_back(it);
  }
  if (ans1.size() < ans2.size()) {
    cout << ans1.size() << endl;
    for (auto it : ans1) cout << it << " ";
    cout << endl;
  } else {
    cout << ans2.size() << endl;
    for (auto it : ans2) cout << it << " ";
    cout << endl;
  }
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long q = 1;
  cin >> q;
  while (q--) {
    solve();
  }
  return 0;
}
