#include <cassert>
#include <cmath>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <functional>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;

using Int = long long;

template <class T1, class T2> ostream &operator<<(ostream &os, const pair<T1, T2> &a) { return os << "(" << a.first << ", " << a.second << ")"; };
template <class T> ostream &operator<<(ostream &os, const vector<T> &as) { const int sz = as.size(); os << "["; for (int i = 0; i < sz; ++i) { if (i >= 256) { os << ", ..."; break; } if (i > 0) { os << ", "; } os << as[i]; } return os << "]"; }
template <class T> void pv(T a, T b) { for (T i = a; i != b; ++i) cerr << *i << " "; cerr << endl; }
template <class T> bool chmin(T &t, const T &f) { if (t > f) { t = f; return true; } return false; }
template <class T> bool chmax(T &t, const T &f) { if (t < f) { t = f; return true; } return false; }


int N;
vector<int> A, B;

vector<vector<int>> graph;
vector<int> us;
vector<int> sz;
int zeit;
vector<int> dis, fin;
void dfs(int u, int p) {
  us.push_back(u);
  sz[u] = 1;
  dis[u] = zeit;
  bool leaf = true;
  for (const int v : graph[u]) if (p != v) {
    leaf = false;
    dfs(v, u);
    sz[u] += sz[v];
  }
  if (leaf) {
    ++zeit;
  }
  fin[u] = zeit;
}

int main() {
  for (int numCases; ~scanf("%d", &numCases); ) { for (int caseId = 1; caseId <= numCases; ++caseId) {
    scanf("%d", &N);
    A.resize(N - 1);
    B.resize(N - 1);
    for (int i = 0; i < N - 1; ++i) {
      scanf("%d%d", &A[i], &B[i]);
      --A[i];
      --B[i];
    }
    
    graph.assign(N, {});
    for (int i = 0; i < N - 1; ++i) {
      graph[A[i]].push_back(B[i]);
      graph[B[i]].push_back(A[i]);
    }
    us.clear();
    sz.assign(N, -1);
    zeit = 0;
    dis.assign(N, -1);
    fin.assign(N, -1);
    dfs(0, -1);
    
    vector<vector<int>> uss(N + 1);
    for (const int u : us) {
      uss[sz[u]].push_back(u);
    }
// cerr<<"us = "<<us<<endl;
// cerr<<"dis = "<<dis<<endl;
// cerr<<"fin = "<<fin<<endl;
// cerr<<"uss = "<<uss<<endl;
    
    vector<int> ans;
    for (int d = 1; d <= N; ++d) {
      bool ok = true;
      int now = 0;
      for (const int u : uss[d]) {
        ok = ok && (now == dis[u]);
        now = fin[u];
      }
      ok = ok && (now == zeit);
      if (ok) {
        ans.push_back(d);
      }
    }
    
    printf("%d\n", (int)ans.size());
    for (int h = 0; h < (int)ans.size(); ++h) {
      if (h) printf(" ");
      printf("%d", ans[h]);
    }
    puts("");
  }
#ifndef LOCAL
  break;
#endif
  }
  return 0;
}