// Write by Daniel Perez .PERAPRO
#include<bits/stdc++.h>

using namespace std;
#define fast_io ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define pb push_back
#define ff first
#define ss second
#define all(s) s.begin(), s.end()
#define mp make_pair
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
using vi=vector<int>;
using vl=vector<ll>;
using pii=pair<int,int>;
char el = '\n';
char esp = ' ';

template<class T> bool ckmin(T& a, const T& b) { return b < a ? a = b, 1 : 0; }
template<class T> bool ckmax(T& a, const T& b) { return a < b ? a = b, 1 : 0; }

template<typename T>
ostream& operator<<(ostream& os, const vector<T> &v){
    for(auto const &i: v){
        os<<i<<" ";
    }
    os<<'\n';
    return os;
}
string yes="YES";
string no="NO";

int pts[] = {1,2,3,4,5,5,4,3,2,1};

int main(){
	fast_io;
	/*
 	freopen("input.txt","r",stdin);
    freopen("output.txt","w",stdout);
    */
    int tc;
    cin>>tc;
    while(tc--){
        int n,m;
        cin>>n>>m;
        
        int root = sqrt(n);
        if(root * root != n) root++;
        
        vector<vi> g(n);
        
        for(int i = 0;i<m;i++){
            int u,v;
            cin>>u>>v;
            u--,v--;
            g[u].pb(v), g[v].pb(u);
        }
        
        set<int> ans;
        vi visited(n);
        function<int(int)> dfs = [&](int u){
            int cur_dis = 0;
            visited[u] = 1;
            for(int v:g[u]){
                if(!visited[v]){
                    ckmax(cur_dis, dfs(v));
                }
            }
            
            if(cur_dis == root){
                ans.insert(u + 1);
                return 0;
            }else{
                return cur_dis + 1;
            }
        };
        
        // cout<<root<<el;
        dfs(0);
        ans.insert(1);
        cout<<ans.size()<<el;
        // for(int i = 0;i<ans.size();i++){
        //     cout<<ans[i]<<esp;
        // }
        for(int u:ans) cout<<u<<esp;
        cout<<el;
    }

}

/*

*/