#include <bits/stdc++.h>  // {{{

// https://codeforces.com/blog/entry/96344

#pragma GCC optimize("O2,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")

using namespace std;

template <typename T>
[[nodiscard]] static T MIN() {
  return std::numeric_limits<T>::min();
}

template <typename T>
[[nodiscard]] static T MAX() {
  return std::numeric_limits<T>::max();
}

template <typename T>
[[nodiscard]] static T sc(auto&& x) {
  return static_cast<T>(x);
}

template <typename T>
[[nodiscard]] static T sz(auto&& x) {
  return static_cast<T>(x.size());
}

#define prln(...) std::println(__VA_ARGS__)
#define pr(...) std::print(__VA_ARGS__)

#ifdef LOCAL
#define dbgln(...) std::println(__VA_ARGS__)
#define dbg(...) std::print(__VA_ARGS__)
#endif

inline static void NO() {
  prln("NO");
}

inline static void YES() {
  prln("YES");
}

using ll = long long;
using ld = long double;
template <typename T>
using ve = std::vector<T>;
template <typename T, size_t N>
using ar = std::array<T, N>;
template <typename T1, typename T2>
using pa = std::pair<T1, T2>;
template <typename... Ts>
using tu = std::tuple<Ts...>;
template <typename... Ts>
using dq = std::deque<Ts...>;
template <typename... Ts>
using qu = std::queue<Ts...>;
template <typename... Ts>
using pq = std::priority_queue<Ts...>;
template <typename... Ts>
using st = std::stack<Ts...>;
auto lb = [](auto... args) {
  return std::lower_bound(args...);
};
auto ub = [](auto... args) {
  return std::upper_bound(args...);
};

#define ff first
#define ss second
#define eb emplace_back
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
//  }}}

void solve() {
  int n;
  cin >> n;
  ve<ll> a(n);
  ve<ll> prefix(n + 1, 0);
  for (int i = 0; i < n; ++i) {
    cin >> a[i];
    prefix[i + 1] = prefix[i] + a[i];
  }

  int l = 0, r = n - 1;
  while (l <= r) {
    int m = l + (r - l) / 2;
    ll weight = prefix[m + 1] - prefix[l];
    cout << "? " << m - l + 1 << '\n';
    for (int x = l; x <= m; ++x)
      cout << ' ' << x + 1;
    ll x;
    cin >> x;
    if (weight == x) {
      l = m + 1;
    } else {
      r = m - 1;
    }
  }

  cout << "! " << l + 1 << '\n';
}

int main() {  // {{{
  int t = 1;
  cin >> t;

  while (t--) {
    solve();
  }

  return 0;
}
// }}}