#include <bits/stdc++.h>
using namespace std;
double tick() {
  static clock_t oldt, newt = clock();
  double diff = 1.0 * (newt - oldt) / CLOCKS_PER_SEC;
  oldt = newt;
  return diff;
}
inline long long int read() {
  long long int f = 1, x = 0;
  char ch = getchar();
  while (ch < '0' || ch > '9') {
    if (ch == '-') f = -1;
    ch = getchar();
  }
  while (ch >= '0' && ch <= '9') {
    x = x * 10 + ch - '0';
    ch = getchar();
  }
  return x * f;
}
long long int fastExpo(long long int a, long long int n) {
  long long int res = 1;
  while (n) {
    if (n % 2) res = res * a;
    n /= 2;
    a = a * a;
  }
  return res;
}
int dx[] = {-1, 0, 1, 0};
int dy[] = {0, 1, 0, -1};
vector<int> v[200010];
int col[200010];
vector<int> l, r;
void dfs(int n, int c) {
  col[n] = c;
  for (int j : v[n]) {
    if (col[j] == -1) dfs(j, 1 - c);
  }
}
int main() {
  int t = read();
  while (t--) {
    int n = read(), m = read();
    while (m--) {
      int a, b;
      cin >> a >> b;
      v[a].push_back(b);
      v[b].push_back(a);
    }
    for (int i = 1; i <= n; i++) col[i] = -1;
    dfs(1, 0);
    long long int c1 = 0, c2 = 0;
    for (int i = 1; i <= n; i++) {
      if (col[i])
        c1++;
      else
        c2++;
    }
    if (c1 <= n / 2) {
      cout << c1 << endl;
      for (int i = 1; i <= n; i++)
        if (col[i]) cout << i << " ";
    } else {
      cout << c2 << endl;
      for (int i = 1; i <= n; i++)
        if (!col[i]) cout << i << " ";
    }
    cout << endl;
    for (int i = 1; i <= n; i++) v[i].clear(), col[i] = -1;
  }
  cerr << "execution time is: " << tick() << "\n";
}
