#include<bits/stdc++.h>
using namespace std;
#define FOR(i,j,k) for(int i=j;i<=k;++i) 
const int MAX = 2e5+111;
int vis[MAX];
vector <int> e[MAX];
int ans[MAX];
int cnt;
int sqrtn;
int dfs(int x){
	int len = 0;
	vis[x]=1;
	for(int nxt:e[x]){
		if(!vis[nxt]){
			len = max(len,dfs(nxt));
		}
	}
	if(len==sqrtn){
		ans[++cnt] = x;
		return 0;
	}
	if(x==1) ans[++cnt] = 1;
	++len;
	return len;
}
signed main(){
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	int T;
	cin>>T;
	while(T--){
		int n,m,x,y;
		cin>>n>>m;
		sqrtn = sqrt(n);
		if(n!=sqrtn*sqrtn) ++sqrtn;
		FOR(i,1,m){
			cin>>x>>y;
			e[x].push_back(y);
			e[y].push_back(x);
		}
		dfs(1);
		cout<<cnt<<endl;
		FOR(i,1,cnt) cout<<ans[i]<<' ';
		cout<<endl;
		cnt = 0;
		FOR(i,1,n) ans[i]=0,vis[i]=0,e[i].clear();
	}
	return 0;
}
/*
1
5 4
1 2
3 2
4 2
5 2
*/