#include <bits/stdc++.h>

#define maxn 1000005

using namespace std;

int n;
vector<int> g[maxn];
vector<int> t[maxn];

int f[maxn];
int siz[maxn];

int cnt;
int tot;
int res[maxn];

void dfs(int u, int fa) {
	f[u] = fa;
	siz[u] = 1;
	for (int v : g[u]) {
		if (v == fa) continue;
		dfs(v, u);
		siz[u] += siz[v];
	}
	if (siz[u] == 1) t[1].push_back(u);
}

int main() {
	int T;
	scanf("%d", &T);
	while (T--) {
		scanf("%d", &n);
		for (int i = 1; i < n; i++) {
			int x, y;
			scanf("%d%d", &x, &y);
			g[x].push_back(y);
			g[y].push_back(x);
		}
		dfs(1, 0);
		cnt = 1;
		res[1] = 1;
		for (int i = 1; i < n; i++) {
			while (!t[i].empty()) {
				int x = t[i].back(); t[i].pop_back();
				if (t[i].empty()) --cnt;
				x = f[x];
				if (t[siz[x]].empty()) ++cnt;
				t[siz[x]].push_back(x);
				if (cnt == 1) res[siz[x]] = 1;
			}
		}
		tot = 0;
		for (int i = 1; i <= n; i++) if (res[i]) ++tot;
		printf("%d\n", tot);
		for (int i = 1; i <= n; i++) if (res[i]) printf("%d ", i);
		puts("");
		for (int i = 1; i <= n; i++) vector<int>().swap(g[i]), vector<int>().swap(t[i]), res[i] = 0;
	}
	return 0;
}