#include <bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>

#define fi first
#define se second
#define p_b push_back
#define pll pair<ll,ll>
#define m_p make_pair
#define all(x) x.begin(),x.end()
#define ld long double
#define sset ordered_set

using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
const ll MAXN = 1123456;

template <typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

template <typename T>
T sqr(T x){
    return x * x;
}

template <typename T>
void vout(T s){
    cout << s << endl;
    exit(0);
}

ll bp(ll a,ll n){
    ll res = 1;
    while(n){
        if(n % 2)res *= a;
        a *= a;
        n >>= 1;
    }
    return res;
}

bool f[MAXN], f1[MAXN];
bool fl;
ll ans;

vector <ll> v[MAXN];

void dfs(ll x, ll pr){
    if(fl)return;
    if(f[x]){
        cout << "A " << x << endl;
        ll c;
        cin >> c;
        if(f1[c]){
            fl = 1;
            ans = c;
            return;
        }
        return;
    }
    for(auto i : v[x])if(i != pr)dfs(i, x);
}

int main(){
    ios_base :: sync_with_stdio(0);
    cin.tie(0);
    //freopen("input.txt","r",stdin);
    //freopen("output.txt","w",stdout);

    ll q;
    cin >> q;
    while(q--){
        ll n;
        cin >> n;
        for(int i = 1; i <= n; i++){
            v[i].clear();
            f[i] = 0;
            f1[i] = 0;
        }

        ll kol;
        kol = n - 1;
        while(kol--){
            ll a, b;
            cin >> a >> b;
            v[a].p_b(b);
            v[b].p_b(a);
        }

        ll m, x;
        cin >> m;
        while(m--){
            cin >> x;
            f[x] = 1;
        }
        cin >> m;
        while(m--){
            cin >> x;
            f1[x] = 1;
        }
        fl = 0;
        cout << "B " << x << endl;
        cin >> x;
        if(f[x])cout << "C " << x << endl; else{
            dfs(x, 0ll);
            if(fl)cout << "C " << ans << endl; else cout << "C -1" << endl;
        }
    }
    cerr << "Time execute: " << clock() / (double)CLOCKS_PER_SEC << " sec" << endl;
    return 0;
}
