#include <bits/stdc++.h>
#define pb push_back
using namespace std;

typedef vector<int> vi;

const int MAXN = 2e5 + 5;
vector<int> G[MAXN];
set<int> S;
int n, m, fa[MAXN], dep[MAXN], tt[MAXN], B;
void dfs(int x, int fz) {
    fa[x] = fz, dep[x] = dep[fz] + 1, tt[x] = dep[x];
    for(int y : G[x]) if(y != fz && fa[y] == -1) 
        dfs(y, x), tt[x] = max(tt[x], tt[y]);
    if(tt[x] - dep[x] + 1 == B) S.insert(x), tt[x] = dep[x] - 1;
}
void solve() {
    cin >> n >> m;
    B = ceil(sqrt(n));
    for(int i = 1; i <= n; i++) fa[i] = -1, G[i].clear();
    for(int i = 1; i <= m; i++) {
        int u, v;
        cin >> u >> v;
        G[u].pb(v), G[v].pb(u);
    }
    S.clear(), dfs(1, 0), S.insert(1);
    cout << S.size() << '\n';
    for(auto o : S) cout << o << ' ';
    cout << '\n';
}
signed main() {
    ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
    int _; for(cin >> _; _; _--) solve();
    return 0;
}