#include <cstdio>
#include <stdio.h>
#include <stdbool.h>
#include <iostream>
#include <map>
#include <vector>
#include <climits>
#include <stack>
#include <string>
#include <queue>
#include <algorithm>
#include <set>
#include <unordered_set>
#include <unordered_map>
#include <cmath>
#include <cctype>
#include <bitset>
#include <iomanip>
#include <cstring>
#include <numeric>
#include <cassert>
#include <random>
#include <chrono>
#include <fstream>
using namespace std;
#define int long long
#define pii pair<int, int>
#define mp make_pair
#define pb push_back
#define fi first
#define se second
int k;
vector<vector<pii> > graph;
vector<int> cc, ans;
vector<set<pii> > s;
void dfs(int node, int par){
for (auto num:graph[node])if (num.fi!=par){
dfs(num.fi, node);
if (s[num.fi].size()>s[node].size())swap(s[num.fi], s[node]);
if (s[num.fi].size()>=k)ans.pb(num.se);
for (auto a:s[num.fi]){
auto it = s[node].lower_bound(mp(a.fi, 0ll));
if (it==s[node].end()||it->fi!=a.fi)s[node].insert(a);
else{
if (a.se+it->se!=cc[it->fi])s[node].insert(mp(a.fi, a.se+it->se));
s[node].erase(it);
}
}
}
}
int32_t main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n, m, a, b;
cin>>n>>m>>k;
graph.resize(n+1);
s.resize(n+1);
for (int i=1; i<n; ++i){
cin>>a>>b;
graph[a].pb(mp(b, i));
graph[b].pb(mp(a, i));
}
cc.resize(m, 0);
for (int i=0; i<m; ++i){
cin>>cc[i];
for (int j=0; j<cc[i]; ++j)cin>>a, s[a].insert(mp(i, 1));
}
dfs(1, 0);
sort(ans.begin(), ans.end());
cout<<ans.size()<<"\n";
for (auto a:ans)cout<<a<<" ";
}
