#include <bits/stdc++.h>

#define all(x) (x).begin(), (x).end()
// #define make_unique(x) sort(all(x)); x.resize(unique(all(x)) - x.begin())

using namespace std;

inline int nxt() {
	int x;
	// scanf("%d", &x);
	cin >> x;
	return x;
}

const int N = 1011111;
vector<int> a[N];
vector<char> can[N];
int sz[N];

void intersect(vector<char>& where, vector<char>& what) {
	if (where.empty()) {
		where.swap(what);
		return;
	}
	if (where.size() > what.size()) {
		where.swap(what);
	}
	for (int i = 0; i < (int)where.size(); ++i) {
		where[i] &= what[i];
	}
}

void dfs(int v, int p = -1) {
	sz[v] = 1;
	for (int x : a[v]) {
		if (x == p) {
			continue;
		}
		dfs(x, v);
		sz[v] += sz[x];
		intersect(can[v], can[x]);
	}
	can[v].resize(sz[v] + 1);
	can[v][sz[v]] = 1;
	// cerr << v + 1 << ": ";
	// for (int i = 1; i <= sz[v]; ++i) {
	// 	cerr << (int)can[v][i];
	// }
	// cerr << "\n";
}

void solve() {
	int n = nxt();
	for (int i = 0; i < n; ++i) {
		a[i] = {};
		can[i] = {};
	}
	for (int i = 0; i < n - 1; ++i) {
		int u = nxt() - 1, v = nxt() - 1;
		a[u].push_back(v);
		a[v].push_back(u);
	}
	dfs(0);
	int cnt = 0;
	for (int i = 1; i <= n; ++i) {
		if (can[0][i]) {
			++cnt;
		}
	}
	cout << cnt << "\n";
	for (int i = 1; i <= n; ++i) {
		if (can[0][i]) {
			cout << i << " ";
		}
	}
	cout << "\n";
}

int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(nullptr);

	int t = nxt();
	for (int i = 1; i <= t; ++i) {
		solve();
	}

	return 0;
}