AC

#include <iostream>
#include <vector>
#include <queue>
#include <cstring>
using namespace std;

const int INF = 1e9; const int MAXN = 40010; // n + m + 2

struct Edge {

int to, cap, rev;

};

vector graph[MAXN]; int level[MAXN], iter[MAXN];

void add_edge(int from, int to, int cap) {

graph[from].push_back({to, cap, (int)graph[to].size()});
graph[to].push_back({from, 0, (int)graph[from].size() - 1});

}

void bfs(int s) {

memset(level, -1, sizeof(level));
queue<int> q;
level[s] = 0;
q.push(s);
while (!q.empty()) {
    int v = q.front(); q.pop();
    for (auto &e : graph[v]) {
        if (e.cap > 0 && level[e.to] < 0) {
            level[e.to] = level[v] + 1;
            q.push(e.to);
        }
    }
}

}

int dfs(int v, int t, int f) {

if (v == t) return f;
for (int &i = iter[v]; i < graph[v].size(); i++) {
    Edge &e = graph[v][i];
    if (e.cap > 0 && level[v] < level[e.to]) {
        int d = dfs(e.to, t, min(f, e.cap));
        if (d > 0) {
            e.cap -= d;
            graph[e.to][e.rev].cap += d;
            return d;
        }
    }
}
return 0;

}

int max_flow(int s, int t) {

int flow = 0;
while (true) {
    bfs(s);
    if (level[t] < 0) return flow;
    memset(iter, 0, sizeof(iter));
    int f;
    while ((f = dfs(s, t, INF)) > 0) {
        flow += f;
    }
}

}

int main() {

ios::sync_with_stdio(false);
cin.tie(nullptr);

int T;
cin >> T;

while (T--) {
    int m, n;
    cin >> m >> n; // m个教室，n个学生
    
    // 初始化图
    for (int i = 0; i <= n + m + 2; i++) {
        graph[i].clear();
    }
    
    int S = 0, T = n + m + 1;
    
    // 源点连接到所有学生
    for (int i = 1; i <= n; i++) {
        add_edge(S, i, 1);
    }
    
    // 所有教室连接到汇点
    for (int i = 1; i <= m; i++) {
        add_edge(n + i, T, 1);
    }
    
    // 读入每个教室可以上课的学生
    for (int i = 1; i <= m; i++) {
        int k;
        cin >> k;
        for (int j = 0; j < k; j++) {
            int student;
            cin >> student;
            // 学生连接到教室
            add_edge(student, n + i, 1);
        }
    }
    
    int flow = max_flow(S, T);
    
    if (flow == m) {
        cout << "YES\n";
    } else {
        cout << "NO\n";
    }
}

return 0;

}