#include <bits/stdc++.h>
using namespace std;
long long t, m, n, a, u, v;
void printAnswer(vector<int> ans) {
  sort(ans.begin(), ans.end());
  cout << ans.size() << endl;
  for (int i = 0; i < ans.size(); i++) {
    cout << ans[i] << " ";
  }
  cout << endl;
}
int main() {
  cin >> t;
  for (int j = 0; j < t; j++) {
    cin >> n >> m;
    vector<vector<int> > G(n + 1);
    for (int i = 0; i < m; i++) {
      cin >> v >> u;
      G[v].push_back(u);
      G[u].push_back(v);
    }
    vector<int> odd;
    vector<int> even;
    bool seen[n + 1];
    for (int i = 0; i <= n; i++) {
      seen[i] = false;
    }
    bool oddLevel = true;
    vector<int> currLevel;
    currLevel.push_back(1);
    seen[1] = true;
    while (currLevel.size() > 0) {
      if (oddLevel) {
        odd.insert(odd.end(), currLevel.begin(), currLevel.end());
      } else {
        even.insert(even.end(), currLevel.begin(), currLevel.end());
      }
      vector<int> nextLevel;
      for (int i = 0; i < currLevel.size(); i++) {
        int n = currLevel[i];
        for (int k = 0; k < G[n].size(); k++) {
          if (!seen[G[n][k]]) {
            seen[G[n][k]] = true;
            nextLevel.push_back(G[n][k]);
          }
        }
      }
      currLevel = nextLevel;
      oddLevel = !oddLevel;
    }
    if (odd.size() >= even.size()) {
      printAnswer(even);
    } else {
      printAnswer(odd);
    }
  }
  return 0;
}
