#include "bits/stdc++.h"
using namespace std;
#define rep(i,a,b) for(int i=(a); i<(b); ++i)
#define all(x) x.begin(),x.end()
#define sz(x) int(x.size())
typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> vi;
typedef vector<vi> vvi;
int main(){
cin.tie(NULL),cin.sync_with_stdio(false);
int n,m,k; cin >> n >> m >> k;
map<pair<int,int>,int> to_input;
vvi adj(n);
rep(i,0,n-1){
int u,v; cin >> u >> v;
u--,v--;
adj[u].push_back(v);
adj[v].push_back(u);
if (u>v) swap(u,v);
to_input[{u,v}] = i;
}
int cc = 0;
vi d(n), vis(n), dfsord(n);
vvi par(__lg(n)+1,vi(n));
auto dfs = [&](int at, int dep, auto&& self) -> void {
vis[at] = 1;
d[at] = dep;
dfsord[at] = cc++;
for(auto to : adj[at]) if (!vis[to]){
par[0][to] = at;
self(to,dep+1,self);
}
};
dfs(0,0,dfs);
rep(i,0,__lg(n)) rep(j,0,n) par[i+1][j] = par[i][par[i][j]];
auto jmp = [&](int at, int k) -> int {
for(int i = 0; k; i++,k/=2) if (k&1) at = par[i][at];
return at;
};
auto lca = [&](int u, int v) -> int {
if (d[u] < d[v]) swap(u,v);
u = jmp(u,d[u]-d[v]);
if (u==v) return u;
for(int i = __lg(n); i>=0; --i)
if (par[i][u] != par[i][v])
u = par[i][u], v = par[i][v];
return par[0][u];
};
vi cnt(n);
auto addpath = [&](int at, int rt) -> void {
cnt[at]++;
cnt[rt]--;
};
rep(i,0,m){
int t; cin >> t;
vi a(t);
rep(j,0,t) cin >> a[j], a[j]--;
sort(all(a),[&](int u, int v){
return dfsord[u] < dfsord[v];
});
int r = t-1;
rep(l,0,t){
int lc = lca(a[l],a[r]);
addpath(a[l],lc);
addpath(a[r],lc);
r = l;
}
}
fill(all(vis),0);
auto prop = [&](int at, auto&& self) -> void {
vis[at] = 1;
for(auto to : adj[at]) if (!vis[to]){
self(to,self);
cnt[at] += cnt[to];
}
};
prop(0, prop);
vi ans;
rep(i,0,n) if (cnt[i] >= k*2) ans.push_back(i);
cout << sz(ans) << '\n';
for(auto c : ans) {
int ot = par[0][c];
if (c > ot) swap(c,ot);
cout << to_input[{c,ot}]+1 << ' ';
}
cout << '\n';
}
/*
9 1 1
1 2
1 3
2 4
2 5
2 6
3 7
6 8
6 9
6 3 2 5 6 8 9
*/
/*
9 1 1
1 2
1 3
2 4
2 5
2 6
3 7
6 8
6 9
5 7 2 5 6 8
*/
/*
13 2 2
1 2
1 3
2 4
2 5
2 6
3 7
6 8
6 9
7 10
1 11
11 12
12 13
9 10 3 8 9 4 13 12 11 1
5 7 2 5 6 8
*/
/*
10 2 2
1 2
2 3
3 4
4 5
5 6
6 7
7 8
8 9
9 10
5 1 3 5 7 9
5 2 4 6 8 10
*/
