#include <bits/stdc++.h>
using namespace std;
int N, M, K;
vector<vector<int>> tree, g;
map<pair<int, int>, int> id;
vector<int> pref;
vector<int> st, en, lvl;
vector<vector<int>> up;
set<int> answer;
void dfs(int u, int dad = 0) {
static int time = 0;
st[u] = ++time;
up[0][u] = dad;
for (int l = 1; (1 << l) <= N; l++) {
up[l][u] = up[l - 1][up[l - 1][u]];
}
for (const int &v : tree[u]) {
if (v != dad) {
lvl[v] = lvl[u] + 1;
dfs(v, u);
}
}
en[u] = time;
}
bool upper(int u, int v) {
return (bool)(st[u] <= st[v] && en[v] <= en[u]);
}
int lca(int u, int v) {
if (upper(u, v)) {
return u;
}
if (upper(v, u)) {
return v;
}
for (int l = ceil(log2(N)); l >= 0; l--) {
if (!upper(up[l][u], v)) {
u = up[l][u];
}
}
return up[0][u];
}
int getVirtualTree(vector<int> &ver) {
sort(ver.begin(), ver.end(), [&](int i, int j) {
return st[i] < st[j];
});
int size = (int)ver.size();
for (int i = 0; i < size - 1; i++) {
ver.push_back(lca(ver[i], ver[i + 1]));
}
sort(ver.begin(), ver.end(), [&](int i, int j) {
return st[i] < st[j];
});
ver.erase(unique(ver.begin(), ver.end()), ver.end());
for (const int &u : ver) {
g[u].clear();
}
vector<int> s;
for (const int &u : ver) {
while ((int)s.size() > 1 && !upper(s.back(), u)) {
g[s[(int)s.size() - 2]].push_back(s.back());
s.pop_back();
}
s.push_back(u);
}
while ((int)s.size() > 1) {
g[s[(int)s.size() - 2]].push_back(s.back());
s.pop_back();
}
return s[0];
}
void dfsVirtual(int u) {
for (const int &v : g[u]) {
pref[u]--;
pref[v]++;
dfsVirtual(v);
}
}
void dfsSums(int u, int dad = -1) {
for (const int &v : tree[u]) {
if (v != dad) {
dfsSums(v, u);
if (pref[v] >= K) {
answer.insert(id[make_pair(u, v)]);
}
pref[u] += pref[v];
}
}
}
int main() {
cin >> N >> M >> K;
tree.resize(N);
g.resize(N);
for (int i = 0; i < N - 1; i++) {
int a, b; cin >> a >> b;
a--; b--;
tree[a].push_back(b);
tree[b].push_back(a);
id[make_pair(a, b)] = id[make_pair(b, a)] = i + 1;
}
st.resize(N);
en.resize(N);
lvl.resize(N);
up.resize(ceil(log2(N)) + 1, vector<int>(N));
lvl[0] = 1;
dfs(0);
pref.resize(N);
for (int i = 0; i < M; i++) {
int V; cin >> V;
vector<int> ver(V);
for (int &u : ver) {
cin >> u;
u--;
}
int virtualRoot = getVirtualTree(ver);
dfsVirtual(virtualRoot);
}
dfsSums(0);
cout << (int)answer.size() << "\n";
for (const int &edge : answer) {
cout << edge << " ";
}
cout << "\n";
return 0;
}
