#include <bits/stdc++.h>
using namespace std;
template <class c>
struct rge {
  c b, e;
};
template <class c>
rge<c> range(c i, c j) {
  return rge<c>{i, j};
}
template <class c>
auto dud(c* x) -> decltype(cerr << *x, 0);
template <class c>
char dud(...);
struct debug {
  template <class c>
  debug& operator<<(const c&) {
    return *this;
  }
};
const int N = 2e5 + 5;
int n, m, t, cnt;
bool firstsign;
vector<vector<int>> edges(N);
vector<bool> isVisited(N, 0), check(N, 0);
void dfs(int v, bool sign) {
  isVisited[v] = true;
  if (sign == firstsign) cnt++;
  check[v] = sign;
  for (auto u : edges[v]) {
    if (!isVisited[u]) {
      dfs(u, !sign);
    }
  }
}
void reset() {
  for (int i = 1; i <= n; i++) {
    edges[i].clear();
    isVisited[i] = false;
    check[i] = false;
  }
  firstsign = false;
  cnt = 0;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cin >> t;
  while (t--) {
    cin >> n >> m;
    reset();
    for (int i = 0; i < m; i++) {
      int x, y;
      cin >> x >> y;
      edges[x].push_back(y);
      edges[y].push_back(x);
    }
    dfs(1, 0);
    if (cnt > n / 2) {
      firstsign = !firstsign;
      cnt = n - cnt;
    }
    cout << cnt << endl;
    for (int i = 1; i <= n; i++) {
      if (check[i] == firstsign) cout << i << " ";
    }
    cout << endl;
  }
  return 0;
}
