#include <bits/stdc++.h>
using namespace std;
bool isPrime(long long int n) {
  if (n <= 1) return false;
  if (n <= 3) return true;
  if (n % 2 == 0 || n % 3 == 0) return false;
  for (long long int i = 5; i * i <= n; i = i + 6)
    if (n % i == 0 || n % (i + 2) == 0) return false;
  return true;
}
long long int gcd(long long int a, long long int b) {
  if (a == 0) return b;
  return gcd(b % a, a);
}
long long int power(long long int x, unsigned long long int y,
                    long long int p) {
  long long int res = 1;
  x = x % p;
  while (y > 0) {
    if (y & 1) res = (res * x) % p;
    y = y >> 1;
    x = (x * x) % p;
  }
  return res;
}
vector<long long int> adj[200005];
long long int dist[200005], visited[200005];
void BFS(long long int src) {
  visited[src] = 1;
  dist[src] = 0;
  queue<long long int> q;
  q.push(src);
  while (!q.empty()) {
    long long int nd = q.front();
    q.pop();
    for (auto it : adj[nd]) {
      if (!visited[it]) {
        visited[it] = 1;
        q.push(it);
        dist[it] = dist[nd] + 1;
      }
    }
  }
}
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long int t;
  cin >> t;
  while (t--) {
    long long int n, m;
    cin >> n >> m;
    for (long long int i = 0; i <= n; i++) {
      dist[i] = 0;
      visited[i] = 0;
      adj[i].clear();
    }
    for (long long int i = 0; i < m; i++) {
      long long int u, v;
      cin >> u >> v;
      adj[u].push_back(v);
      adj[v].push_back(u);
    }
    BFS(1);
    long long int e = 0, o = 0;
    for (long long int i = 1; i <= n; i++) {
      if (dist[i] % 2 == 0)
        e++;
      else
        o++;
    }
    vector<long long int> ans;
    if (e < o) {
      for (long long int i = 1; i <= n; i++) {
        if (dist[i] % 2 == 0) ans.push_back(i);
      }
    } else {
      for (long long int i = 1; i <= n; i++) {
        if (dist[i] % 2 != 0) ans.push_back(i);
      }
    }
    cout << ans.size() << endl;
    for (auto it : ans) cout << it << " ";
    cout << endl;
  }
  return 0;
}
