#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define deb(x) cout << #x << "=" << x << endl
#define pb push_back
#define mp make_pair
#define all(x) x.begin(), x.end()
#define sortall(x) sort(all(x))
#define tr(it, a) for (auto it = a.begin(); it != a.end(); it++)
#define mod 1000000007
const int N = 1e5 + 7;
int mx;
int n;
vector<int> answer;
vector<int> adj[N];
void construct_bfs_tree(vector<vector<int>> &tree)
{
    queue<int> q;
    q.push(1);
    vector<bool> vis(n, false);
    vis[1] = true;
    while (!q.empty())
    {
        int node = q.front();
        q.pop();
        for (auto it : adj[node])
        {
            if (!vis[it])
            {
                tree[node].push_back(it);
                tree[it].push_back(node);
                vis[it] = true;
                q.push(it);
            }
        }
    }
}
void dfs(int node, int par, int distance, vector<vector<int>> &tree)
{
    if (distance > mx)
    {
        answer.push_back(node);
        distance = 0;
    }

    for (auto it : tree[node])
    {
        if (it != par)
        {
            dfs(it, node, distance + 1, tree);
        }
    }
}
int main()
{
#ifndef ONLINE_JUDGE
    freopen("a.in", "r", stdin);
    freopen("a.out", "w", stdout);
#endif
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int t;
    cin >> t;
    while (t--)
    {
        answer.clear();
        cin >> n;
        int m;
        cin >> m;
        mx = (int)ceil(sqrt(n));
        for (int i = 1; i <= n; i++)
        {
            adj[i].clear();
        }
        for (int i = 1; i <= m; i++)
        {
            int u, v;
            cin >> u >> v;
            adj[u].push_back(v);
            adj[v].push_back(u);
        }
        vector<vector<int>> tree(n + 1);
        construct_bfs_tree(tree);
        // for (int u = 1; u <= n; u++)
        // {

        //     for (int v : tree[u])
        //     {
        //         if (v < u)
        //             continue;
        //         cout << u << " " << v << endl;
        //     }
        // }
        dfs(1, 0, 0, tree);
        answer.push_back(1);
        cout << (int)answer.size() << endl;
        for (int a : answer)
        {
            cout << a << " ";
        }
    }
    return 0;
}