#include <bits/stdc++.h>

#define IO	       { ios_base::sync_with_stdio(false); cin.tie(0); }

using namespace std;



int n, m;
vector<set<int>> adj;
vector<int> subtree_size;

int get_subtree_size(int node, int parent = -1) {
	int &res = subtree_size[node];
	res = 1;
	for (int i : adj[node]) {
		if (i == parent) { continue; }
		res += get_subtree_size(i, node);
	}
	return res;
}

int get_centroid(int node, int sz, int parent = -1) {
	for (int i : adj[node]) {
		if (i == parent) { continue; }

		if (subtree_size[i] * 2 > sz) { return get_centroid(i, sz, node); }
	}
	return node;
}


vector<vector<int>> adj2;
vector<bool> vis;

void dfs(int node) {
    vis[node] = 1;
    for (int v: adj2[node]) {
        if (!vis[v]) {
            adj[v].insert(node);
            adj[node].insert(v);
            dfs(v);
        }
    }
}

int lim;

vector<int> cs;

void rec(int v) {
    int sz = get_subtree_size(v);
    if (subtree_size[v] <= lim) return;
    int x = get_centroid(v, sz);
    //cout << "C = " << x + 1 << endl;
    cs.push_back(x);
    for (int y: adj[x]) {
        adj[y].erase(x);
        rec(y);
    }
}

void solve() {
    cin >> n >> m;
    for (int i=1; ;i++) {
        if (i*i >= n) {
            lim = i;
            break;
        }
    }
    
    adj.clear();
    adj2.clear();
    adj.resize(n+100);
    adj2.resize(n+100);
    subtree_size.assign(n+100, 0);
    vis.assign(n+100, 0);

	for (int i = 0; i < m; i++) {
		int a, b;
		cin >> a >> b;
		a--;
		b--;
        adj2[a].push_back(b);
        adj2[b].push_back(a);
	}

    dfs(0);
   
    cs.clear();
    rec(0);
    cout << cs.size() << endl;
    for (int x: cs) {
        cout << x + 1 << " ";
    }
    cout << endl;
}

int main() {
    IO;
    int t;
    cin >> t;
    while(t--) {
        solve();
    }
}