#include <bits/stdc++.h>

const int N = 2e5 + 5;
std::vector<int> g[N];
int n, m, dep[N];
bool vis[N];

void solve() {
  scanf("%d%d", &n, &m);
  for (int i = 1; i <= n; i++) g[i].clear();

  for (int u, v, i = 1; i <= m; i++) {
    scanf("%d%d", &u, &v);
    g[u].push_back(v);
    g[v].push_back(u);
  }

  memset(vis + 1, 0, n * sizeof(bool));
  auto dfs = [&](int x, int f, auto &dfs) -> void {
    if (vis[x]) return;
    vis[x] = 1, dep[x] = dep[f] + 1;
    for (auto y : g[x]) dfs(y, x, dfs);
  };
  dfs(1, 0, dfs);

  int t = ceil(sqrt(n));
  std::vector<int> S;
  for (int i = 1; i <= n; i++) {
    if ((dep[i] - 1) % t == 0) S.push_back(i);
  }

  assert(S.size() <= t);
  printf("%u\n", S.size());
  for (auto x : S) printf("%d ", x);
  puts("");
}

signed main() {
  int t;
  scanf("%d", &t);
  while (t--) solve();
}