#include <bits/stdc++.h>
using namespace std;
#define lli long long int

void createTree(vector<int>& tree, vector<vector<int>>& adjList, vector<bool>& visited, int current, int height, priority_queue<pair<int,int>>& pq)
{
    visited[current] = true;
    pq.push({height, current});
    for (int index = 0; index < adjList[current].size(); index++)
    {
        auto& dest = adjList[current][index];
        if (!(visited[dest]))
        {
            tree[dest] = current;
            createTree(tree, adjList, visited, dest, height + 1, pq);
        }
        else
        {
            dest = -1;
        }
    }
}

void markVisited(int current, vector<bool>& visited, vector<vector<int>>& adjList)
{
    if (!(visited[current]))
    {
        visited[current] = true;
        for (auto dest : adjList[current])
        {
            if (dest == -1){continue;}
            markVisited(dest, visited, adjList);
        }
    }
}

void solveCase()
{
    int v,e; cin >> v >> e;
    vector<bool> visited(v,false);
    vector<vector<int>> adjList(v);
    for (int i = 0; i < e; i++)
    {
        int a1, a2; cin >> a1 >> a2; a1--; a2--;
        adjList[a1].push_back(a2);
        adjList[a2].push_back(a1);
    }
    // Create tree
    vector<int> tree(v, 0);
    priority_queue<pair<int,int>> pq;
    createTree(tree, adjList, visited, 0, 0, pq);
    int distance = (int)(ceil(sqrt((double)(v))));
    visited = vector<bool>(v, false);
    vector<int> solution;
    while (!(pq.empty()))
    {
        int current = pq.top().second; pq.pop();
        if (visited[current]){continue;}
        for (int i = 0; i < distance; i++)
        {
            current = tree[current];
        }
        solution.push_back(current);
        markVisited(current, visited, adjList);
    }
    cout << solution.size() << "\n";
    cout << solution[0] + 1;
    for (int i = 1; i < solution.size(); i++)
    {
        cout << " " << solution[i] + 1;
    }
    cout << "\n";
}

int main()
{
    int nCases; cin >> nCases;
    while (nCases--)
    {
        solveCase();
    }
}