#include<bits/stdc++.h>
#define inf 1e9
#define eps 1e-6
#define FOR(i,a,b) for(int i=a;i<=b;i++)
#define REP(i,a,b) for(int i=a;i>=b;i--)
#define db double
#define ve vector<int>
#define pa pair<int,int>
#define fr first
#define sd second
#define pb push_back
#define mp make_pair
#define MEM(a) memset(a,0,sizeof(a))
typedef long long ll;
typedef unsigned long long ull;
using namespace std;
inline ll read()
{
	char ch = getchar();
	ll s = 0, w = 1;
	while (ch < '0' || ch > '9') {if (ch == '-')w = -1; ch = getchar();}
	while (ch >= '0' && ch <= '9') {s = s * 10 + ch - '0'; ch = getchar();}
	return s * w;
}
#define N 1000010
int n;
vector<int>e[N];
int id[N], sz[N];
map<int, bool>ma[N];
vector<int>V;
void dfs(int x, int fa)
{
	sz[x] = 1; int fl = 0;
	for (int y : e[x])if (y != fa)
		{
			dfs(y, x);
			sz[x] += sz[y];
			if (!fl)swap(ma[x], ma[y]), fl = 1;
			else
			{
				if (ma[x].size() < ma[y].size())swap(ma[x], ma[y]); V.clear();
				for (auto [t, _] : ma[y])if (ma[x][t]) {V.push_back(t);}
				ma[x].clear(); for (int t : V)ma[x][t] = 1;
			}
		}
	ma[x][sz[x]] = 1;
}
void sol()
{
	cin >> n;
	for (int i = 1; i <= n - 1; i ++)
	{
		int x, y;
		cin >> x >> y;
		e[x].push_back(y), e[y].push_back(x);
	}
	dfs(1, 0);
	vector<int>ans;
	for (int i = 1; i <= n; i ++)if (ma[1][i])ans.push_back(i);
	cout << ans.size() << '\n';
	for (int x : ans)cout << x << ' '; cout << '\n';
	for (int i = 1; i <= n; i ++)e[i].clear(), ma[i].clear();
}
signed main()
{
	//freopen(".in","r",stdin);
	//freopen(".out","w",stdout);
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	int T; cin >> T;
	while (T --)sol();
	return 0;
}