#include <bits/stdc++.h>
using namespace std;

const int N = 25 + 10;
int n, m, fa[N], dep[N], p[N], B, f[N];
bool v[N];
vector<int> G[N];

void dfs(int x) {
	f[x] = 0;
	for (int y : G[x]) if (!dep[y]) {
		dep[y] = dep[x] + 1, fa[y] = x;
		dfs(y);
		f[x] = max(f[x], f[y] + 1);
	}
	if (f[x] >= B) {
		v[x] = true;
		f[x] = 0;
	}
}

void solve() {
	cin >> n >> m;
	for (int i = 1; i <= n; i ++)
		v[i] = false, G[i].clear(), fa[i] = 0, dep[i] = 0;
	B = ceil(sqrt(n));
	for (int i = 1, x, y; i <= m; i ++)
		cin >> x >> y, G[x].push_back(y), G[y].push_back(x);
	dep[1] = 1;
	dfs(1);
	vector<int> ans;
	for (int i = 1; i <= n; i ++) if (v[i])
		ans.push_back(i);
	assert(ans.size() <= B);
	cout << ans.size() << "\n";
	for (int x : ans)
		cout << x << " ";
	cout << "\n";
}

int main() {
	ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
	int tt; cin >> tt;
	while (tt --) solve();
	return 0;
}