#include <iostream>
#include <cstdio>
#include <cmath>
#include <map>
#include <algorithm>
#include <vector>
#include <cctype>
#include <queue>
using namespace std;
typedef long long ll;
const int maxn=200005;
const int INF=0x7f7f7f7f;

inline int read(){
    int x=0,w=1;char c=getchar();
    for(;!isdigit(c);c=getchar())if(c=='-')w=-1;
    for(;isdigit(c);x=(x<<3)+(x<<1)+c-'0',c=getchar());
    return x*w;
}

inline ll readll(){
    ll x=0,w=1;char c=getchar();
    for(;!isdigit(c);c=getchar())if(c=='-')w=-1;
    for(;isdigit(c);x=(x<<3)+(x<<1)+c-'0',c=getchar());
    return x*w;
}

int n,m,k;
vector<int>vct[maxn],st;
int dep[maxn];
int fa[maxn],vis[maxn]; 

int dfs(int u,int f){
	dep[u]=dep[f]+1;
	int mx=dep[u];
	for(int i=0;i<vct[u].size();i++){
		int v=vct[u][i];
		if(v==f||fa[v])continue;
		fa[v]=u;
		mx=max(mx,dfs(v,u));
	}
	if(mx-dep[u]==k){
		st.push_back(u);
		return 0;
	}
	return mx;
}
int main(){
	int t=read();
	for(;t--;){
		n=read(),m=read();
		k=(int)sqrt(n)*(int)sqrt(n)<n?(sqrt(n)+1):sqrt(n);
		for(int i=1;i<=m;i++){
			int u=read(),v=read();
			vct[u].push_back(v);
			vct[v].push_back(u);
		}
		int mx=dfs(1,0);
		if(st.size()<k)
		printf("%d\n",st.size());
		for(int i=1;i<=st.size();i++){
			printf("%d ",st[i-1]);
		}
		printf("\n");
		st.clear();	
		for(int i=1;i<=n;i++)vct[i].clear(),dep[i]=fa[i]=0;
	} 
	
	
	return 0;
}