#include<bits/stdc++.h>
#define int long long
using namespace std;
int T,n,m,B;
vector<int>to[200010];
int fa[200010];
vector<int>ans;
int Find(int i){
	return fa[i] == i ? i : fa[i] = Find(fa[i]);
}
void Unite(int u,int v){
	u = Find(u),v = Find(v);
	if(u == v) return;
	fa[u] = v;
}
void dfs(int u,int fa,int tmp){
	if(tmp == B + 1) ans.push_back(u),tmp = 0;
	for(auto v : to[u]){
		if(v == fa) continue;
		dfs(v,u,tmp + 1);
	}
}
mt19937 rnd(time(0));
signed main(){
	scanf("%lld",&T);
	while(T--){
		scanf("%lld %lld",&n,&m);
		for(int i = 1; i <= n; i++) to[i].clear(),fa[i] = i;
		for(int i = 1,u,v; i <= m; i++){
			scanf("%lld %lld",&u,&v);
			if(Find(u) != Find(v)) to[u].push_back(v),to[v].push_back(u),Unite(u,v);
		}
		B = ceil(sqrt(n));
		while(1){
			ans.clear();
			int rt = rnd() % n + 1;
			dfs(rt,0,B + 1);
			if((int)(ans.size()) <= B){
				printf("%lld\n",(int)(ans.size()));
				for(auto v : ans) printf("%lld ",v);
				printf("\n");
				break;
			} 
		}
	}
	return 0;
}