#include<bits/stdc++.h>
using namespace std;

const int N=2e5+1e3+7;

int T,n,m,L;

vector<int>g[N];

int vis[N],d[N];

vector<int>ans;

void dfs(int x)
{
    d[x]=1e9;
    for(auto v:g[x])
    {
        if(vis[v])
            continue;
        vis[v]=1;
        dfs(v);
        d[x]=min(d[x],d[v]+1);
    }
    if(d[x]>L)
        ans.push_back(x),d[x]=0;
}

int main()
{
    scanf("%d",&T);
    while(T--)
    {
        scanf("%d%d",&n,&m);
        L=0;
        while(L*L<n)
            L++;
        for(int i=1;i<=n;i++)
            vis[i]=0,g[i].clear();
        ans.clear();
        for(int i=1;i<=m;i++)
        {
            int u,v;
            scanf("%d%d",&u,&v);
            g[u].push_back(v);
            g[v].push_back(u);
        }
        vis[1]=1;
        dfs(1);
        printf("%d\n",(int)ans.size());
        for(int i=0;i<ans.size();i++)
            printf("%d%c",ans[i]," \n"[i+1==ans.size()]);
    }
}