#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#pragma GCC target("avx,avx2,fma")
using namespace std;
void __print(int x) { cerr << x; }
void __print(long x) { cerr << x; }
void __print(long long x) { cerr << x; }
void __print(unsigned x) { cerr << x; }
void __print(unsigned long x) { cerr << x; }
void __print(unsigned long long x) { cerr << x; }
void __print(float x) { cerr << x; }
void __print(double x) { cerr << x; }
void __print(long double x) { cerr << x; }
void __print(char x) { cerr << '\'' << x << '\''; }
void __print(const char *x) { cerr << '\"' << x << '\"'; }
void __print(const string &x) { cerr << '\"' << x << '\"'; }
void __print(bool x) { cerr << (x ? "true" : "false"); }
template <typename T, typename V>
void __print(const pair<T, V> &x) {
  cerr << '{';
  __print(x.first);
  cerr << ',';
  __print(x.second);
  cerr << '}';
}
template <typename T>
void __print(const T &x) {
  int f = 0;
  cerr << '{';
  for (auto &i : x) cerr << (f++ ? "," : ""), __print(i);
  cerr << "}";
}
void _print() { cerr << "]\n"; }
template <typename T, typename... V>
void _print(T t, V... v) {
  __print(t);
  if (sizeof...(v)) cerr << ", ";
  _print(v...);
}
const long long int MOD = 1e9 + 7;
const long long int INF = 1000000000;
const long long int MAX_N = 2e5 + 2;
vector<int> adj[MAX_N], vis(MAX_N), ans[2];
void dfs(int node, int col) {
  vis[node] = 1;
  ans[col].push_back(node);
  for (auto x : adj[node]) {
    if (!vis[x]) dfs(x, col ^ 1);
  }
}
void solve() {
  int n, e;
  cin >> n >> e;
  ans[0].clear();
  ans[1].clear();
  for (int i = 0; i < n + 1; ++i) adj[i].clear(), vis[i] = 0;
  int a, b;
  for (int i = 0; i < e; ++i) {
    cin >> a >> b;
    adj[a].push_back(b), adj[b].push_back(a);
  }
  dfs(1, 0);
  if (ans[0].size() > ans[1].size()) swap(ans[0], ans[1]);
  cout << ans[0].size() << "\n";
  for (auto x : ans[0]) cout << x << " ";
  cout << "\n";
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  ;
  int t;
  cin >> t;
  while (t--) solve();
}
