#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> ii;
typedef pair<ii, ll> iii;
#define pb push_back
#define fi first
#define se second
#define endl '\n'
#define MASK(i) (1ll << (i))
#define BIT(x, i) (((x) >> (i)) & 1)
const ll MOD = 1e9+7;
ll n,q,k;
ll cnt;
ll h[100005];
ll par[100005][20];
ll st[100005];
ll en[100005];
ll f[100005];
vector <ii> res;
vector <ll> a[100005];
map <ii,ll> mp;
bool cmp(ll a,ll b){
return st[a] < st[b];
}
void dfs(ll x,ll p){
st[x] = ++cnt;
for (ll i : a[x]){
if (i == p) continue;
h[i] = h[x] + 1;
par[i][0] = x;
dfs(i,x);
}
en[x] = cnt;
}
void setup(){
for (long j=1; j<=18; j++){
for (long i=1; i<=n; i++) par[i][j] = par[par[i][j-1]][j-1];
}
h[0] = -1;
}
ll lck(ll u,ll v){
if (h[u] < h[v]) swap(u,v);
for (long i=18; i>=0; i--){
if (h[par[u][i]] >= h[v]) u = par[u][i];
}
if (u == v) return u;
for (long i=18; i>=0; i--){
if (par[u][i] != par[v][i]){
u = par[u][i];
v = par[v][i];
}
}
return par[u][0];
}
void dfs2(ll x,ll p){
for (ll i : a[x]){
if (i == p) continue;
dfs2(i,x);
f[x] += f[i];
}
if (f[x] >= 2 * k) res.pb({x,par[x][0]});
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
cin >> n >> q >> k;
for (long i=1; i<n; i++){
ll u,v; cin >> u >> v;
a[u].pb(v);
a[v].pb(u);
mp[{u,v}] = mp[{v,u}] = i;
}
h[1] = 1;
dfs(1,0);
setup();
while (q--){
ll ski; cin >> ski;
vector <ll> adj;
for (long i=1; i<=ski; i++){
ll x; cin >> x;
adj.pb(x);
}
sort(adj.begin(),adj.end(),cmp);
adj.pb(adj[0]);
for (long i=1; i<adj.size(); i++){
ll x = adj[i-1];
ll y = adj[i];
f[x]++;
f[y]++;
f[lck(x,y)] -= 2;
}
}
dfs2(1,0);
cout << res.size() << endl;
for (ii i : res){
ll x = i.fi;
ll y = i.se;
cout << mp[{i.fi,i.se}] << ' ';
}
}
