#include<bits/stdc++.h>

using namespace std;

#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()

using ll = long long;

const int N = 2e5 + 5;
const int K = 449;

vector<int> gr[N];

int d[N], used[N];
const int inf = 1e9;
int k;
vector<int> ans;

void dfs(int v, int p) {
    used[v] = 1;
    int mx = 0;
    int ch = 0;
    for (int u: gr[v]) {
        if (used[u] == 0){
            dfs(u, v);
            ch++;
            mx = max(mx, d[u]);
        }

    }
    if (ch == 0) {
        d[v] = 0;
    }else{
        if (mx + 1 >= k) {
            ans.push_back(v + 1);
            d[v] = -1;
        } else {
            if(v == 0 && sz(ans) == 0)
                ans.push_back(v + 1);
            d[v] = mx + 1;
        }
    }

}

void solve() {
    int n, m;
    cin >> n >> m;
    k = ceil(sqrt(n));
    {
        ans.clear();
        for (int i = 0; i < n; i++)
            gr[i].clear(), used[i] = 0, d[i] = 0;
    }
    for (int i = 0; i < m; i++) {
        int u, v;
        cin >> u >> v;
        u--, v--;
        gr[u].push_back(v);
        gr[v].push_back(u);
    }

    dfs(0,-1);

    cout << sz(ans) << '\n';
    for (int i: ans) {
        cout << i << ' ';
    }
    cout << '\n';
}

int main() {
#ifndef LOCAL
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
#else
    freopen("input.txt", "r", stdin);
#endif
    int t;
    cin >> t;
    while (t--)
        solve();
    return 0;
}