#include<bits/stdc++.h>
using namespace std;
const int N = 5e5+10;
vector<int> e[N];
vector<int> ans;
int dis[N];
int n, m, k;
int x ,y;
bool vis[N];
bool bfs(int x){
     for(int i = 1;i <= n;i++) vis[i] = 0;
     queue<int> q;
     dis[x] = 0;
     q.push(x);
     ans.clear();
    while(!q.empty()){
        int u = q.front();
        q.pop();
        for(auto y : e[u]){
            if(vis[y]) continue;
            vis[y] = 1;
            dis[y] = dis[u] + 1;
            q.push(y);
        }
    }
    for(int i = 1;i <= n;i++){
        if(dis[i]%(k+1) == 1){
            ans.push_back(i);
        }
    }
    //if(ans.size() == 0)Q ans.push_back(1);
    if(ans.size()  <= k)
    return 1;
    return 0;
}
int main(){
    int tt;
    cin >> tt;
    while(tt--){
        cin >> n >>m;
        ans.clear();
        for(int i = 0;i <= n;i++){
                e[i].clear();
            vis[i] = 0;
            dis[i] = 0;
        }
        k = ceil(sqrt(n));
        for(int i = 1;i <= m;i++){
            cin >> x >> y;
            e[x].push_back(y);
            e[y].push_back(x);
        }
        for(int i = 1; i<= n;i++){
         bool f = bfs(i);
         if(f){
        cout << ans.size() << "\n";
        for(auto x : ans){
            cout << x << " ";
        }
        cout << "\n";
        break;
        }
        }
    }
    return 0;
}
/*
1000
11 19
8 11
4 11
2 11
2 3
8 3
6 1
6 4
11 5
5 3
10 8
7 10
4 7
3 9
5 1
5 7
3 6
10 1
11 7
2 9

70 109
32 69
26 15
65 46
70 62
50 23
17 16
15 31
2 23
18 11
48 57
19 29
52 42
26 31
7 1
53 66
5 69
58 20
59 38
3 4
9 53
7 56
52 66
66 28
22 51
2 6
22 35
5 28
25 51
27 13
26 56
10 50
53 56
60 48
67 33
61 23
*/