#include <bits/stdc++.h> 
using namespace std;
#define f first
#define s second
int main(){
	long long zz;
	cin>>zz;
	while(zz--){
		long long n,m;
		cin>>n>>m;
		vector<long long> adj[n+1];
		vector<bool> visited(n+1,0);
		vector<long long> depth(n+1,-1);
		set<long long> stt;
		long long  bor;
		for(long long i=0;i<=n;i++){
			if(i*i>=n){
				bor=i;
				break;
			}
		}
		for(long long i=0;i<m;i++){
		long long x,y;
		cin>>x>>y;
		x--;y--;
		adj[x].push_back(y);
		adj[y].push_back(x);
		}
		bool flag=1;
		while(flag){
		stt.clear();
		queue<long long> q;
		int y=(rand()%n);
		q.push(y);
		depth[y]=y;
		stt.insert(y);
		while(!q.empty()){
			long long store=-1;
		while(!q.empty()){
			long long v=q.front();
			q.pop();
			visited[v]=1;
			if(depth[v]==bor){
				store=v;
				depth[v]=0;
				break;
			}
			for(auto x:adj[v]){
				if(!visited[x]){
				depth[x]=1+depth[v];
				q.push(x);
				}
			}
		}
		while(!q.empty()){
			q.pop();
		}
		if(store==-1){
			for(long long i=0;i<n;i++){
				if(!visited[i]){
					q.push(i);
					depth[i]=0;
					stt.insert(i);
					break;
				}
			}
		}
		else{
			q.push(store);
			stt.insert(store);
		}
		}
		if(stt.size()<=bor){
		cout<<stt.size()<<'\n';
		for(auto x: stt){
			cout<<1+x<<' ';
		}
		cout<<'\n';
		flag=0;
		}
		}
		
	}
	
	return 0;
}