#include <bits/stdc++.h>
using namespace std;
vector<vector<long long int>> adj(2e5 + 5);
vector<vector<long long int>> a(2e5 + 5);
vector<long long int> c;
vector<bool> b(1e5 + 5);
class dop {
 public:
  long long int n, m, x, y;
  vector<long long int> d;
  void get();
};
void dop::get() {
  cin >> n >> m;
  vector<vector<long long int>> adj(n + 1);
  vector<long long int> c(n + 1);
  vector<long long int> b(n + 1);
  for (long long int i = 0; i < m; i++) {
    cin >> x >> y;
    adj[x].push_back(y);
    adj[y].push_back(x);
  }
  for (long long int i = 0; i < n + 1; i++) {
    c.push_back(1e18);
  }
  c[1] = 0;
  for (long long int i = 1; i <= n; i++) {
    b[i] = false;
  }
  b[1] = true;
  queue<long long int> q;
  q.push(1);
  c[1] = 0;
  while (!q.empty()) {
    x = q.front();
    q.pop();
    for (auto u : adj[x]) {
      if (!b[u]) {
        b[u] = true;
        c[u] = c[x] + 1;
        q.push(u);
      }
    }
  }
  x = y = 0;
  for (long long int i = 1; i <= n; i++) {
    if (c[i] % 2 == 0) {
      x++;
    } else {
      y++;
    }
  }
  if (x > y) {
    cout << y << '\n';
    for (long long int i = 1; i <= n; i++) {
      if (c[i] % 2 != 0) {
        cout << i << " ";
      }
    }
    cout << '\n';
  } else {
    cout << x << '\n';
    for (long long int i = 1; i <= n; i++) {
      if (c[i] % 2 == 0) {
        cout << i << " ";
      }
    }
    cout << '\n';
  }
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long int t;
  cin >> t;
  dop obj[t];
  for (long long int i = 0; i < t; i++) {
    obj[i].get();
  }
  return 0;
}
