#include <bits/stdc++.h>
#include <ios>
#define ll long long int
#define ii pair<int, int>
#define ff first
#define ss second
#define vi vector<ll>
#define lli long long
#define vii vector<ii>
#define pb push_back
#define fast_io                                                                \
  ios_base::sync_with_stdio(0);                                                \
  cin.tie(0);                                                                  \
  cout.tie(0);
using namespace std;

const int N = 2e5;
const ll MOD = 1e9 + 7;
const int oo = 1e9 + 7;
vi dis;
vector<bool> vis;
vector<vi> g;
int k;
vi ans;

int dfs(int s) {
  vis[s] = 1;
  int mxDis = 1;
  for (int veci : g[s]) {
    if (vis[veci])
      continue;
    mxDis = max(1 + dfs(veci), mxDis);
  }
  if (mxDis == k + 1) {
    ans.pb(s);
    mxDis = 0;
  }
  return mxDis;
}

int main() {
  int tc;
  cin >> tc;
  while (tc--) {
    int n, m;
    cin >> n >> m;
    g.clear();
    g.resize(n);
    k = sqrt(n);
    if (k * k != n)
      k++;
    for (int i = 0; i < m; i++) {
      int u, v;
      cin >> u >> v;
      u--;
      v--;
      g[u].pb(v);
      g[v].pb(u);
    }
    vis.assign(n, false);
    ans.resize(0);
    dfs(0);
    if (ans.size() < k)
      ans.pb(0);
    cout << ans.size() << endl;
    for (int i : ans) {
      cout << i + 1 << " ";
    }
    cout << endl;
  }
  return 0;
}