#include <bits/stdc++.h>
using namespace std;
#ifdef MIKU
const string dbmc = "\033[1;38;2;57;197;187m", dbrs = "\033[0m";
#define debug(x...) cout << dbmc << '[' << #x << "] : ", dout(x)
void dout() { cout << dbrs << endl; }
template <typename T, typename ...U>
void dout(T t, U ...u) { cout << t << (sizeof...(u) ? ", " : ""); dout(u...); }
#else
#define debug(...) 39
#endif
#define int long long
#define fs first
#define sc second
#define mp make_pair
#define FOR(i, j, k) for (int i = j, Z = k; i < Z; i++)
typedef pair<int, int> pii;
const int MXN = 100005;
int n, m, k, c, s[MXN];
int eu[MXN], ev[MXN];
vector<int> eid[MXN];
struct CLR {
int clr[MXN], ans;
void init(int n) {
fill(clr + 1, clr + n + 1, 0);
ans = 0;
}
void ADD(int a) {
if (++clr[a] == 1) ans++;
}
void SUB(int a) {
if (--clr[a] == 0) ans--;
}
} clr;
namespace HLD {
int d[MXN], p[MXN], sz[MXN], son[MXN], top[MXN], dfn[MXN], C;
int rdfn[MXN], ep[MXN];
vector<int> vc[MXN];
void DFS1(int id, int par, int dep) {
p[id] = par;
d[id] = dep;
sz[id] = 1;
son[id] = -1;
for (auto &e : eid[id]) {
int i = eu[e] ^ ev[e] ^ id;
if (i == par) continue;
ep[i] = e;
DFS1(i, id, dep + 1);
sz[id] += sz[i];
if (son[id] == -1) son[id] = i;
else if (sz[son[id]] < sz[i]) son[id] = i;
}
}
void DFS2(int id, int par, int _t) {
top[id] = _t;
rdfn[C] = id;
dfn[id] = C++;
if (son[id] != -1) DFS2(son[id], id, _t);
for (auto &e : eid[id]) {
int i = eu[e] ^ ev[e] ^ id;
if (i == par) continue;
if (i == son[id]) continue;
DFS2(i, id, i);
}
}
void DO(int rt) {
DFS1(1, 0, 0);
DFS2(1, 0, 1);
}
void ADD(int x, int y, int c) {
while (top[x] != top[y]) {
if (d[top[x]] < d[top[y]]) swap(x, y);
vc[dfn[top[x]]].push_back(c);
vc[dfn[x] + 1].push_back(-c);
x = p[top[x]];
}
if (d[x] < d[y]) swap(x, y);
vc[dfn[y] + 1].push_back(c);
vc[dfn[x] + 1].push_back(-c);
}
void BOX(vector<int> &v, int k) {
clr.init(m);
FOR(i, 0, n) {
for (auto &j : vc[i]) {
if (j > 0) clr.ADD(j);
else clr.SUB(-j);
}
if (clr.ans >= k) v.push_back(ep[rdfn[i]]);
}
}
}
void miku() {
cin >> n >> m >> k;
FOR(i, 1, n) {
cin >> eu[i] >> ev[i];
eid[eu[i]].push_back(i);
eid[ev[i]].push_back(i);
}
HLD::DO(1);
FOR(j, 1, m + 1) {
cin >> c;
FOR(i, 0, c) cin >> s[i];
FOR(i, 1, c) HLD::ADD(s[0], s[i], j);
}
vector<int> ans;
HLD::BOX(ans, k);
sort(ans.begin(), ans.end());
cout << ans.size() << '\n';
for (auto &i : ans) cout << i << ' ';
cout << '\n';
}
int32_t main() {
cin.tie(0) -> sync_with_stdio(false);
cin.exceptions(iostream::failbit);
miku();
return 0;
}
