#include <bits/stdc++.h>

using namespace std;

int main() {
#ifdef wxh010910
  freopen("input.txt", "r", stdin);
#endif
  int tt;
  scanf("%d", &tt);
  while (tt--) {
    int n;
    scanf("%d", &n);
    vector<vector<int>> adj(n);
    for (int i = 0; i < n - 1; ++i) {
      int x, y;
      scanf("%d %d", &x, &y);
      --x;
      --y;
      adj[x].push_back(y);
      adj[y].push_back(x);
    }
    vector<int> color(n);
    vector<int> ans(n);
    vector<int> sz(n);
    function<void(int)> rev = [&](int x) {
      ans[x] ^= 1;
      for (auto y : adj[x]) {
        rev(y);
      }
    };
    function<void(int, int)> dfs = [&](int x, int pr) {
      if (~pr) {
        adj[x].erase(find(adj[x].begin(), adj[x].end(), pr));
      }
      sz[x] = 1;
      for (auto y : adj[x]) {
        color[y] = !color[x];
        dfs(y, x);
        sz[x] ^= sz[y];
      }
      if (adj[x].empty()) {
        ans[x] = 1;
      } else if (adj[x].size() == 1) {
        ans[x] = !ans[adj[x][0]];
      } else {
        ans[x] = sz[x];
        int cur = !sz[x];
        for (auto y : adj[x]) {
          if (ans[y] != cur) {
            rev(y);
          }
          if (sz[y]) {
            cur = !cur;
          }
        }
      }
    };
    dfs(0, -1);
    int sum = 0;
    for (int i = 0; i < n; ++i) {
      sum += color[i];
    }
    if (sum == n / 2) {
      puts("1");
      vector<int> foo, bar;
      for (int i = 0; i < n; ++i) {
        if (color[i]) {
          foo.push_back(i);
        } else {
          bar.push_back(i);
        }
      }
      for (int i = 0; i < n / 2; ++i) {
        printf("%d%c", foo[i] + 1, i == n / 2 - 1 ? '\n' : ' ');
      }
      for (int i = 0; i < n / 2; ++i) {
        printf("%d%c", bar[i] + 1, i == n / 2 - 1 ? '\n' : ' ');
      }
    } else {
      puts("2");
      vector<int> foo, bar;
      for (int i = 0; i < n; ++i) {
        if (ans[i]) {
          foo.push_back(i);
        } else {
          bar.push_back(i);
        }
      }
      for (int i = 0; i < n / 2; ++i) {
        printf("%d%c", foo[i] + 1, i == n / 2 - 1 ? '\n' : ' ');
      }
      for (int i = 0; i < n / 2; ++i) {
        printf("%d%c", bar[i] + 1, i == n / 2 - 1 ? '\n' : ' ');
      }
    }
  }
  return 0;
}