#include<bits/stdc++.h>
#define ll long long
#define ull unsigned long long
#define maxn 200005
#define put() putchar('\n')
#define Tp template<typename Ty>
#define Ts template<typename Ty,typename... Ar>
using namespace std;
void read(int &x){
    int f=1;x=0;char c=getchar();
    while (c<'0'||c>'9') {if (c=='-') f=-1;c=getchar();}
    while (c>='0'&&c<='9') {x=x*10+c-'0';c=getchar();}
    x*=f;
}
namespace Debug{
	Tp void _debug(char* f,Ty t){cerr<<f<<'='<<t<<endl;}
	Ts void _debug(char* f,Ty x,Ar... y){while(*f!=',') cerr<<*f++;cerr<<'='<<x<<",";_debug(f+1,y...);}
	Tp ostream& operator<<(ostream& os,vector<Ty>& V){os<<"[";for(auto& vv:V) os<<vv<<",";os<<"]";return os;}
	#define gdb(...) _debug((char*)#__VA_ARGS__,__VA_ARGS__)
}using namespace Debug;
#define fi first
#define se second
#define mk make_pair
const int mod=1e9+7;
int power(int x,int y=mod-2) {
	int sum=1;
	while (y) {
		if (y&1) sum=sum*x%mod;
		x=x*x%mod;y>>=1;
	}
	return sum;
}
int n,m;
vector<int>to[maxn];
int vis[maxn],ans[maxn],cnt,block,total;
void dfs(int x,int deep) {
	if (deep==-1) ans[++cnt]=x,deep=block;
 	vis[x]=1;
	for (auto y:to[x]) if (!vis[y]) {
		dfs(y,deep-1);
	}
}
const int N=19;
void solve(void) {
	int i,x,y;
	read(n);read(m);
	block=sqrt(n);block+=(block*block!=n);
	for (i=1;i<=n;i++) to[i].clear(),vis[i]=0;cnt=0;
	for (i=1;i<=m;i++) {
		if (total==N) printf("%d %d  ",x,y);
		read(x),read(y);
		to[x].push_back(y);
		to[y].push_back(x);
	}
	if (total==N) return ;
	dfs(1,block-1);
	if (cnt==0) ans[cnt=1]=1;
	if (cnt>block) {
		printf("%d %d\n",n,m);
		exit(0);
	}
	printf("%d\n",cnt);
	for (i=1;i<=cnt;i++) printf("%d ",ans[i]);put();
}
signed main(void){
	++total;
	int T;read(T);while (T--) solve(),++total;
	return 0;
}