#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1e5 + 25;
int n, m, k;
vector <int> adj[MAXN];
int t = 0;
int in[MAXN], out[MAXN], dep[MAXN], p[MAXN];
void dfs (int pos, int par = 0) {
in[pos] = ++t;
p[pos] = par;
for (auto j : adj[pos]) {
if (j == par) continue;
dep[j] = 1 + dep[pos];
dfs(j, pos);
}
out[pos] = t;
}
int dp[18][MAXN];
int jump (int a, int b) {
for (int i = 17; i >= 0; i--) {
if (b & (1 << i)) {
a = dp[i][a];
}
}
return a;
}
int lca (int a, int b) {
if (dep[a] > dep[b]) swap(a, b);
b = jump(b, dep[b] - dep[a]);
if (a == b) return a;
for (int i = 17; i >= 0; i--) {
int x = dp[i][a], y = dp[i][b];
if (x && y && x != y) {
a = x; b = y;
}
}
return jump(a, 1);
}
map <int, int> vals[MAXN];
void insert (int a, int b, int c) {
if (a == b) return;
vals[a][c]++;
vals[b][c]--;
}
vector <int> kk;
void dfs2 (int pos, int par) {
for (auto j : adj[pos]) {
if (j == par) continue;
dfs2(j, pos);
if (vals[j].size() > vals[pos].size()) vals[j].swap(vals[pos]);
for (auto p : vals[j]) {
vals[pos][p.first] += p.second;
if (vals[pos][p.first] == 0) vals[pos].erase(p.first);
}
vals[j].clear();
}
if (vals[pos].size() >= k) {
kk.push_back(pos);
}
}
map <pair <int, int>, int> lll;
int main () {
cin >> n >> m >> k;
for (int i = 1; i < n; i++) {
int a, b;
cin >> a >> b;
adj[a].push_back(b);
adj[b].push_back(a);
lll[{a, b}] = lll[{b, a}] = i;
}
dfs(1);
for (int i = 1; i <= n; i++) dp[0][i] = p[i];
for (int j = 1; j <= 17; j++) {
for (int i = 1; i <= n; i++) {
dp[j][i] = dp[j - 1][dp[j - 1][i]];
}
}
while (m--) {
int x;
cin >> x;
vector <int> dd(x);
for (auto &i : dd) cin >> i;
sort(dd.begin(), dd.end(), [&] (int a, int b) {
return in[a] < in[b];
});
for (int i = 1; i < (int)dd.size(); i++) {
int x = lca(dd[i], dd[i - 1]);
insert(dd[i], x, m);
insert(dd[i - 1], x, m);
}
}
dfs2(1, -1);
cout << (int)kk.size() << '\n';
for (auto &i : kk) {
i = lll[{i, p[i]}];
}
sort(kk.begin(), kk.end());
for (auto i : kk) cout << i << " ";
}
