#include <bits/stdc++.h>
#define pb push_back
#define rep(i, j, k) for(int i = j; i <= k; ++ i)
#define per(i, j, k) for(int i = j; i >= k; -- i)
using namespace std;
using ll = long long;
const int N = 3e5 + 10;
int n, m, d[N];
vector<int> G[N], T[N];
bool vis[N], ban[N], fir;
void dfs(int u, int fa = 0) {
    vis[u] = true;
    d[u] = 0;
    for(int v: G[u]) if(!vis[v]) {
        T[u].pb(v);
        dfs(v, u);
    }
}

void dfs2(int u) {
    d[u] = 0;
    for(int v: T[u]) if(!ban[v]) {
        dfs2(v);
        d[u] = max(d[u], d[v] + 1);
    }
}

void Ban(int u) {
    ban[u] = true;
    for(int v: T[u]) if(!ban[v]) Ban(v);
}

int main() {
    int test;
    scanf("%d", &test);
    rep(_, 1, test) {
        scanf("%d%d", &n, &m);
        int s = (int)(sqrt(n) + 0.2);
        rep(i, 1, n) G[i].clear(), T[i].clear(), vis[i] = ban[i] = false;
        rep(i, 1, m) {
            int u, v;
            scanf("%d%d", &u, &v);
            G[u].pb(v);
            G[v].pb(u);
        }
        dfs(1);
        vector<int> ans;
        while(1) {
            dfs2(1);
            if(d[1] <= s) {
                ans.pb(1);
                break;
            }
            for(int i = 1; i <= n; i ++)
                if(!ban[i] && d[i] == s) {
                    ans.pb(i);
                    Ban(i);
                    break;
                }
        }
        printf("%d\n", (int)ans.size());
        for(int v: ans) {
            printf("%d ", v);
        }
        puts("");
    }
    return 0;
}