#include <bits/stdc++.h>
using namespace std;
#define int long long
#define show(x,y) //cout << y << " " << #x << "\n";
#define show2(x,y,i,j) //cout << y << " " << #x << " " << j << " " << #i << "\n";
typedef pair<int,int>pii;
void solve(){
}
int n,m,k;
vector<pii>adj[100005];
int color[100005];
const int MAXN = 100050;
const int LOGN = 17;
int p[LOGN+1][MAXN], h[MAXN]; //h: number of edges from root
long long d[MAXN]; //dist: sum of edge weight from root
bitset<MAXN> visited;
void dfs(int x) {
if (visited[x]) return;
visited[x] = 1;
for (int k = 0; k < LOGN; ++k) {
if (p[k][x] == -1) break;
p[k+1][x] = p[k][p[k][x]];
}
for (auto it:adj[x]) {
if (visited[it.first]) continue;
p[0][it.first] = x;
d[it.first] = d[x] + 1;
h[it.first] = h[x] + 1;
color[it.first]=it.second;
dfs(it.first);
}
}
/* Query */
int lca(int a, int b) { //h[a] < h[b]
if (h[a] > h[b]) swap(a, b);
/* advance b by h[b] - h[a] parents */
for (int k = 0, d = h[b] - h[a]; k < LOGN; ++k) {
if (d & (1<<k)) b = p[k][b];
}
if (a == b) return a;
assert(h[a] == h[b]); //same height
/* to be continued */
for (int k = LOGN-1; k >= 0; --k) {
if (p[k][a] != p[k][b])
a = p[k][a], b = p[k][b];
}
assert(p[0][a] == p[0][b]); //same immediate parent
return p[0][a];
}
set<pii>storage[100005]; //end ind
vector<int>ans;
void dp(int index, int par){
for(auto it:adj[index]){
if(it.first==par) continue;
dp(it.first,index);
show(neigh,it.first);
if(storage[it.first].size()>storage[index].size()) swap(storage[it.first],storage[index]);
for(auto it2:storage[it.first]) storage[index].insert(it2);
}
show(visit,index);
//remove end nodes
auto ite=storage[index].lower_bound({index,0});
while(ite!=storage[index].end()&&ite->first==index){
storage[index].erase(ite);
ite=storage[index].lower_bound({index,0});
}
if(storage[index].size()>=k){
ans.push_back(color[index]);
}
}
int32_t main(){
//ios::sync_with_stdio(0);
//cin.tie(0);
cin >> n >> m >> k;
int temp,temp2;
for(int x=0;x<n-1;x++){
cin >> temp >> temp2;
adj[temp].push_back({temp2,x+1});
adj[temp2].push_back({temp,x+1});
}
dfs(1);
show(done,1);
for(int x=0;x<m;x++){
cin >> temp;
vector<int>v;
for(int y=0;y<temp;y++){
cin >> temp2;
v.push_back(temp2);
}
int ancestor=v[0];
for(int y=1;y<temp;y++){
ancestor=lca(ancestor,v[y]);
}
for(int y=0;y<temp;y++){
storage[v[y]].insert({ancestor,x});
}
}
show(done,2);
dp(1,-1);
show(done,3);
cout << ans.size() << "\n";
for(auto it:ans){
cout << it << " ";
}
}
