#include <bits/stdc++.h>
using namespace std;
typedef int (*uniopi)(int);
typedef long long (*uniopl)(long long);
typedef int (*binopi)(int, int);
typedef long long (*binopl)(long long, long long);
typedef int (*tupopi)(int, int, int);
typedef long long (*tupopl)(long long, long long, long long);
const long double PI = acos(0) * 2;
const int INF = 0x3f2f1f0f;
const long long LINF = 1ll * INF * INF;
int X4[] = {-1, 0, 1, 0}, Y4[] = {0, -1, 0, 1};
int X8[] = {-1, -1, -1, 0, 1, 1, 1, 0}, Y8[] = {-1, 0, 1, 1, 1, 0, -1, -1};
template <typename T>
inline bool uax(T& a, T b) {
  return a < b ? (a = b, 1) : 0;
}
template <typename T>
inline bool uin(T& a, T b) {
  return a > b ? (a = b, 1) : 0;
}
template <typename T1, typename T2>
istream& operator>>(istream& is, pair<T1, T2>& p) {
  return is >> p.first >> p.second;
}
template <typename T1, typename T2>
ostream& operator<<(ostream& os, const pair<T1, T2>& p) {
  return os << '(' << p.first << ", " << p.second << ")";
}
template <typename T>
ostream& operator<<(ostream& os, const vector<T>& v) {
  for (int i = 0; i < (int)v.size(); i++) {
    os << v[i];
    if (i + 1 < (int)v.size()) os << ' ';
  }
  return os;
}
void dfs(int a, vector<vector<int> >& ed, vector<int>& cr) {
  int c1 = 0, c2 = 0;
  for (auto& b : ed[a]) {
    if (cr[b] == 1)
      c1++;
    else if (cr[b] == 2)
      c2++;
  }
  if (c1 == 0)
    cr[a] = 1;
  else
    cr[a] = 2;
  for (auto& b : ed[a]) {
    if (!cr[b]) dfs(b, ed, cr);
  }
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(nullptr);
  cout << std::setprecision(10);
  cout << fixed;
  int q;
  cin >> q;
  while (q--) {
    int n, m;
    cin >> n >> m;
    vector<vector<int> > ed(n + 1, vector<int>());
    vector<int> cr(n + 1, 0);
    while (m--) {
      int a, b;
      cin >> a >> b;
      ed[a].push_back(b);
      ed[b].push_back(a);
    }
    dfs(1, ed, cr);
    int c1 = 0, c2 = 0;
    for (int i = 1; i <= (n); i++) {
      if (cr[i] == 1)
        c1++;
      else
        c2++;
    }
    if (c1 <= n / 2) {
      cout << c1 << endl;
      for (int i = 1; i <= (n); i++)
        if (cr[i] == 1) cout << i << ' ';
      cout << endl;
    } else {
      cout << c2 << endl;
      for (int i = 1; i <= (n); i++)
        if (cr[i] == 2) cout << i << ' ';
      cout << endl;
    }
  }
  return 0;
}
