#include <bits/stdc++.h>
using namespace std;
long long power(long long x, long long y, long long p) {
  long long res = 1;
  x = x % p;
  while (y > 0) {
    if (y & 1) res = (res * x) % p;
    y = y >> 1;
    x = (x * x) % p;
  }
  return res;
}
long long visited[300050], count1, count2;
std::vector<long long> edge[300050];
void dfs(long long s) {
  for (auto it : edge[s]) {
    if (!visited[it]) {
      if (visited[s] == 1)
        visited[it] = 2;
      else
        visited[it] = 1;
      dfs(it);
    }
  }
  count1 += (visited[s] == 1);
  count2 += (visited[s] == 2);
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  long long t, i, j, n, m, k, q, temp, x, y;
  cin >> t;
  while (t--) {
    count1 = 0, count2 = 0;
    long long count = 0;
    bool flag = 0;
    long long a[200050] = {0};
    string s;
    cin >> n >> m;
    for (int i = 0; i < m; i++) {
      cin >> x >> y;
      edge[x].push_back(y);
      edge[y].push_back(x);
    }
    visited[1] = 1;
    dfs(1);
    if (count1 <= count2) {
      cout << count1 << endl;
      for (i = 1; i <= n; i++) {
        if (visited[i] == 1) {
          cout << i << " ";
        }
        edge[i].clear();
        visited[i] = 0;
      }
    } else {
      cout << count2 << endl;
      for (i = 1; i <= n; i++) {
        if (visited[i] == 2) {
          cout << i << " ";
        }
        edge[i].clear();
        visited[i] = 0;
      }
    }
    cout << endl;
  }
  return 0;
}
