#include <bits/stdc++.h>
using namespace std;
template <typename A, typename B>
string to_string(pair<A, B> p);
template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p);
template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p);
string to_string(const string& s) { return '"' + s + '"'; }
string to_string(const char* s) { return to_string((string)s); }
string to_string(bool b) { return (b ? "true" : "false"); }
string to_string(vector<bool> v) {
  bool first = true;
  string res = "{";
  for (int i = 0; i < static_cast<int>(v.size()); i++) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(v[i]);
  }
  res += "}";
  return res;
}
template <size_t N>
string to_string(bitset<N> v) {
  string res = "";
  for (size_t i = 0; i < N; i++) {
    res += static_cast<char>('0' + v[i]);
  }
  return res;
}
template <typename A>
string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto& x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}
template <typename A, typename B>
string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}
template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " +
         to_string(get<2>(p)) + ")";
}
template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " +
         to_string(get<2>(p)) + ", " + to_string(get<3>(p)) + ")";
}
void debug_out() { cerr << endl; }
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}
const long long INF = 1e9 + 7;
const long long N = 2e3 + 5;
const long double EPS = 1e-12;
const long long MOD = 1e9 + 7;
void solve() {
  long long n;
  cin >> n;
  vector<vector<long long>> g(n + 1);
  unordered_map<long long, bool> mp1, mp2;
  for (long long i = 0; i + 1 < n; i++) {
    long long u, v;
    cin >> u >> v;
    g[u].push_back(v);
    g[v].push_back(u);
  }
  long long k1;
  cin >> k1;
  for (long long i = 0; i < k1; i++) {
    long long first;
    cin >> first;
    mp1[first] = 1;
  }
  long long k2;
  cin >> k2;
  for (long long i = 0; i < k2; i++) {
    long long first;
    cin >> first;
    mp2[first] = 1;
  }
  cout << "B " << mp2.begin()->first << endl;
  long long s;
  cin >> s;
  vector<bool> was(n + 1);
  was[s] = 1;
  queue<long long> q;
  q.push(s);
  while (!q.empty()) {
    long long v = q.front();
    q.pop();
    42;
    if (mp1[v]) {
      cout << "A " << v << endl;
      long long r;
      cin >> r;
      if (mp2[r]) {
        cout << "C " << v << endl;
      } else {
        cout << "C -1" << endl;
      }
      return;
    }
    for (auto& i : g[v]) {
      if (!was[i]) {
        q.push(i);
        was[i] = 1;
      }
    }
  }
  cout << "C -1" << endl;
}
signed main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  long long tests = 1;
  cin >> tests;
  while (tests-- > 0) {
    solve();
  }
  return 0;
}
