//Δ_D
#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
typedef double DB;
const int N = 222222;
int n,m,k,f[N],b[N];
vector<int> v[N],s;
void dfs(int u){
	b[u]=1;
	int i,x;
	for(i=0;i<v[u].size();i++){
		x=v[u][i];
		if(!b[x]){
			dfs(x);
			f[u]=max(f[u],f[x]+1);
		}
	}
	if(f[u]==k||u==1)
		f[u]=0,s.push_back(u);
}
int main(){
	int T,i,x,y;
	scanf("%d",&T);
	while(T--){
		scanf("%d%d",&n,&m);
		while(m--){
			scanf("%d%d",&x,&y);
			v[x].push_back(y);
			v[y].push_back(x);
		}
		for(k=1;k*k<n;k++);
		dfs(1);
		printf("%d\n",s.size());
		for(i=0;i<s.size();i++)
			printf("%d ",s[i]);
		printf("\n");
		s.clear();
		for(i=1;i<=n;i++)
			v[i].clear(),b[i]=0;
	}
	return 0;
}