#pragma GCC optimize(3,"Ofast","inline")
#pragma GCC optimize(2)
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define pb push_back
#define rep(i,a,b) for(ll i=a;i<=b;++i)
typedef pair<ll,ll> pll;
const ll N=4e5+5;
vector<ll>vec[N],vcc[N];
ll t,n,m,k,tt,tp;
ll vis[N];
ll B;
void dfs(ll u,ll pre)
{
    if(vis[u])return ;
    vis[u]=1;
    if(pre!=0)
    {
        vcc[u].pb(pre);
        vcc[pre].pb(u);
    }
    for(auto v:vec[u])if(v!=pre)dfs(v,u);
}
vector<ll>v;
ll dep[N],vc[N];
ll dfss(ll u,ll pre)
{
    ll dp=1;
    for(auto v:vcc[u])if(v!=pre)
    {
        dp=max(dp,dfss(v,u)+1);
    }
    if(dp==B)
    {
        v.pb(u);
        return -1;
    }
    return dp;
}
int	 main(){
    ios::sync_with_stdio(0); cin.tie(0);
	int T=1;
	cin>>T;
	while(T--)
    {
        cin>>n>>m;
        v.clear();
        rep(i,1,n)
        {
            vis[i]=vc[i]=0;
            vec[i].clear(),vcc[i].clear();
        }
        rep(i,1,m)
        {
            ll u,v;
            cin>>u>>v;
            vec[u].pb(v);
            vec[v].pb(u);
        }
        dfs(1,0);
        B=(ll)sqrt(n-1.0)+1;
        dfss(1,0);
        if(v.empty())v.pb(1);
        assert(v.size()<=B);
        cout<<v.size()<<"\n";
        for(auto x:v)cout<<x<<" ";
        cout<<"\n";
    }
}
/*
2
4 3
1 2
2 3
3 4

6 7
1 2
2 3
3 1
1 4
4 5
5 6
6 4
*/