#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <string>
#include <cstring>
#include <cmath>
#include <ctime>
#include <algorithm>
#include <utility>
#include <stack>
#include <queue>
#include <vector>
#include <set>
#include <math.h>
#include <map>
#include <sstream>
#include <deque>
#include <unordered_map>
#include <unordered_set>
#include <bitset>
#include <stdio.h>
#include <iostream>
#include <vector>
#include <queue>
#include <array>
#include <climits>
using namespace std;
#define   LL long long
#define ls o<<1
#define rs o<<1|1
#define PII pair<int,int>
#define PPI pair<pair<int,int>,int >
const int N = 2e5 + 1000;
const LL  mod = 998244353;
const LL MAX = 1e18;
vector<int> g[N];
int n, m;
int fa[N], ans[N], cn = 0, d,dep[N],maxx=0;
int father(int x)
{
    if (fa[x] != x)
        fa[x] = father(fa[x]);
    return fa[x];
}
int dfs(int u, int fa)
{   
    dep[u] = dep[fa] + 1;
    maxx = max(maxx, dep[u]);
    int fg = 0,cx=0;
    for (int v : g[u]) 
    {

        if (v == fa) continue;
        cx=max(cx,dfs(v, u)+1);
        fg = 1;
    }
    if (cx == d) 
    {
        ans[++cn] = u;
        return 0;
    }
    if (!fg) return 1;
    return cx;
}
void solve()
{
    scanf("%d%d", &n, &m);
    for (int i = 1; i <= n; i++) dep[i]=0, fa[i] = i, g[i].clear();
    for (int i = 1; i <= m; i++)
    {
        int u, v;
        scanf("%d%d", &u, &v);
        int fau = father(u), fav = father(v);
        if (fau != fav)
        {
            fa[fau] = fav;
            g[u].push_back(v);
            g[v].push_back(u);  

        }
    }
    d = sqrt(n);
    if (d * d < n) d++;
    dep[1] = -1;
    maxx = 0;
    cn = 0;
    dfs(1, 1);
    if (maxx<d) 
    {
        printf("1\n");
        printf("1\n");
        return  ;
    }
    printf("%d\n", cn);
    for (int i = 1; i <= cn; i++)
        printf("%d ", ans[i]);
    printf("\n");
    return;
}
int main()
{

    int T = 1;
    cin >> T;
    while (T--)
        solve();
    return 0;
}