#include<bits/stdc++.h>
#define rep(i,n) for(int i=1;i<=n;++i)
#define eb emplace_back
#define st first
#define nd second
using namespace std;
using ll=long long;
using ld=long double;
using i128=__int128;
using pii=pair<int,int>;
const ld eps=1e-12;
const int N=2e5+5;
int T,n,m;
vector<int>g[N];
int f[N],ord[N],top,tim[N];
vector<int>ans;
void dfs(int x,int fa){
    f[x]=fa;ord[++top]=x;
    for(int v:g[x])if(f[v]==-1)dfs(v,x);
}
int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    for(cin>>T;T--;){
        cin>>n>>m;
        int lim=0;
        while(lim*lim<n)++lim;
        rep(i,n)g[i].clear(),f[i]=-1,tim[i]=lim;
        top=0;
        ans.clear();

        rep(i,m){
            int x,y;
            cin>>x>>y;
            g[x].eb(y),g[y].eb(x);
        }
        dfs(1,0);
        for(int i=n;i;--i){
            int x=ord[i];
            if(tim[x]==2*lim||(x==1&&tim[x]>lim)){
                ans.eb(x);
                tim[x]=0;
            }
            tim[f[x]]=max(tim[f[x]],tim[x]+1);
        }
        cout<<ans.size()<<"\n";
        for(int x:ans)cout<<x<<"\n";
    }
    return 0;
}
/*
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
*/