#include "bits/stdc++.h"
#define fast ios_base::sync_with_stdio(0) , cin.tie(0) , cout.tie(0)
#define endl '\n'
#define int long long
#define f first
#define mp make_pair
#define s second
using namespace std;
int n, m, k;
int fa[100005][21], par[100005], dep[100005], arr[150005];
set <int> vals[100005], ans;
vector <int> g[100005], rem[100005], add[100005];
unordered_map<int, unordered_map<int,int> > edge;
void dfs(int x, int d, int p){
dep[x] = d;
par[x] = p;
for(int k : g[x]){
if(k != p) dfs(k, d + 1, x);
}
}
int LCA(int a, int b){
if(dep[a] > dep[b]) swap(a, b);
int d = dep[b] - dep[a];
for(int i = 0; i < 20; i++){
if(d & (1 << i)) b = fa[b][i];
}
if(a == b) return a;
for(int i = 20; i >= 0; i--){
if(fa[a][i] != fa[b][i]){
a = fa[a][i];
b = fa[b][i];
}
}
return par[a];
}
void solve(int node, int parent){
int big = node;
for(int i : g[node]){
if(i == parent) continue;
solve(i, node);
if(vals[i].size() > vals[big].size()) big = i;
if(vals[i].size() >= k) ans.insert(edge[node][i]);
}
swap(vals[node], vals[big]);
for(int i : g[node]){
if(i == parent) continue;
for(int x : vals[i]) vals[node].insert(x);
}
for(int i : add[node]) vals[node].insert(i);
for(int i : rem[node]) vals[node].erase(i);
}
signed main()
{
fast;
cin >> n >> m >> k;
for(int i = 0; i < n-1; i++){
int a, b;
cin >> a >> b;
g[a].push_back(b);
g[b].push_back(a);
edge[a][b] = edge[b][a] = i;
}
dfs(1, 1, -1);
par[1] = 1;
for(int i = 1; i <= n; i++) fa[i][0] = par[i];
for(int k = 0; k < 20; k++){
for(int i = 1; i <= n; i++){
fa[i][k+1] = fa[fa[i][k]][k];
}
}
for(int i = 0; i < m; i++){
int t; cin >> t;
int y = 0;
for(int j = 0; j < t; j++){
cin >> arr[j];
y = (j == 0 ? arr[j] : LCA(y, arr[j]));
}
rem[y].push_back(i);
for(int j = 0; j < t; j++) add[arr[j]].push_back(i);
}
solve(1, -1);
cout << ans.size() << endl;
for(int i : ans) cout << i + 1 << ' ';
cout << endl;
}
