#include<bits/stdc++.h>
#define pll pair<ll, ll>
using namespace std;
typedef long long ll;
#define int ll

const int N = 2e5+10;
const int M = 1e6 + 7;

int n, m, fa[N], mx;
vector<ll> edge[N], ans;
bool vis[N];
void init(){
    for (int i = 0; i <= n; i++)fa[i] = i, edge[i].clear(),vis[i]=0;
    ans.clear();
    mx = sqrt(n);
    if (mx * mx < n)mx++;
}

int dfs(int u,int dis){
    if(dis>mx){
        ans.push_back(u);
        dis=0;
    }
    for(int v:edge[u]){
        if(vis[v])continue;
        vis[v]=1;
        dis=min(dfs(v,dis+1),dis);
    }
    return dis+1;
}




inline void solve(){
    cin >> n >> m;
    init();

    for (int i = 1, u, v; i <= m; i++){
        cin >> u >> v;
        edge[u].push_back(v);
        edge[v].push_back(u);
    }
    ans.push_back(1);
    dfs(1,0);
    cout<<ans.size()<<"\n";for(int i:ans)cout<<i<<" ";cout<<"\n";
}



signed main(){
    ios::sync_with_stdio(false),cin.tie(0),cout.tie(0);
    int WTN666=1;cin>>WTN666;
    while(WTN666--){
        solve();
    }
}