#include <bits/stdc++.h>
using namespace std;
template <class T>
void _R(T &x) {
  cin >> x;
}
void _R(int &x) { scanf("%d", &x); }
void _R(long long &x) { scanf("%lld", &x); }
void _R(unsigned long long &x) { scanf("%llu", &x); }
void _R(double &x) { scanf("%lf", &x); }
void _R(char &x) { scanf(" %c", &x); }
void _R(char *x) { scanf("%s", x); }
void R() {}
template <class T, class... U>
void R(T &head, U &...tail) {
  _R(head);
  R(tail...);
}
template <class T>
void _W(const T &x) {
  cout << x;
}
void _W(const int &x) { printf("%d", x); }
void _W(const long long &x) { printf("%lld", x); }
void _W(const double &x) { printf("%.16f", x); }
void _W(const char &x) { putchar(x); }
void _W(const char *x) { printf("%s", x); }
template <class T, class U>
void _W(const pair<T, U> &x) {
  _W(x.first);
  putchar(' ');
  _W(x.second);
}
template <class T>
void _W(const vector<T> &x) {
  for (auto i = x.begin(); i != x.end(); _W(*i++))
    if (i != x.cbegin()) putchar(' ');
}
void W() {}
template <class T, class... U>
void W(const T &head, const U &...tail) {
  _W(head);
  putchar(sizeof...(tail) ? ' ' : '\n');
  W(tail...);
}
const int MAXN = 2e6 + 10, MAXM = 1e6 + 10;
const int INF = INT_MAX, SINF = 0x3f3f3f3f;
const long long llINF = LLONG_MAX;
const int MOD = 1e9 + 7, mod = 998244353;
const int inv2 = 5e8 + 4;
const int Lim = 1 << 20;
int dis[MAXN], mxdis, n;
vector<int> g[MAXN];
pair<int, int> query(vector<int> &ask) {
  W('?', ((int)ask.size()), ask);
  fflush(stdout);
  pair<int, int> tmp;
  R(tmp.first, tmp.second);
  return tmp;
}
int sum, cen;
void dfs(int u, int f) {
  for (auto v : g[u])
    if (v != f) {
      dis[v] = dis[u] + 1;
      mxdis = max(mxdis, dis[v]);
      dfs(v, u);
    }
}
pair<int, int> chk(int mid) {
  vector<int> ask;
  for (int i = 1; i <= n; i++)
    if (dis[i] == mid) ask.push_back(i);
  if (ask.empty()) return {-1, -1};
  pair<int, int> tmp = query(ask);
  return tmp;
}
int dis1, dis2, nd1, nd2;
bool vis[MAXN], flag = 0;
void dfs2(int u, int f) {
  if (u == nd1) {
    flag = vis[u] = 1;
    return;
  }
  for (auto v : g[u])
    if (v != f) {
      dfs2(v, u);
      if (flag) {
        vis[u] = 1;
        return;
      }
    }
}
void solve() {
  R(n);
  memset(dis, 0, (n + 10) * sizeof(int));
  mxdis = 0;
  memset(vis, 0, n + 5);
  flag = 0;
  for (int i = 1; i <= n; i++) g[i].resize(0);
  for (int i = 1; i < n; i++) {
    int u, v;
    R(u, v);
    g[u].push_back(v);
    g[v].push_back(u);
  }
  vector<int> ask;
  for (int i = 1; i <= n; i++) ask.push_back(i);
  pair<int, int> tmp = query(ask);
  cen = tmp.first, sum = tmp.second;
  ask.resize(0);
  dfs(cen, 0);
  int l = sum / 2 - 1, r = min(sum, mxdis);
  dis1 = 0, nd1 = 0;
  while (l <= r) {
    int mid = (l + r) >> 1;
    tmp = chk(mid);
    if (tmp.second == sum)
      l = mid + 1, dis1 = mid, nd1 = tmp.first;
    else
      r = mid - 1;
  }
  dfs2(cen, 0);
  for (int i = 1; i <= n; i++)
    if (dis[i] == sum - dis1 && !vis[i]) ask.push_back(i);
  if (((int)ask.size())) {
    tmp = query(ask);
    nd2 = tmp.first;
  } else
    nd2 = cen;
  W("!", nd1, nd2);
  fflush(stdout);
  string s;
  R(s);
  fflush(stdout);
}
int main() {
  int T = 1;
  R(T);
  while (T--) solve();
  return 0;
}
