#include <bits/stdc++.h>

using namespace std;
#define IOS ios::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr)
#define rep(a, b, c) for(int (a)=(b);(a)<=(c);(a)++)
#define per(a, b, c) for(int (a)=(b);(a)>=(c);(a)--)
#define mset(var, val) memset(var,val,sizeof(var))
#define ll long long
#define int ll
#define fi first
#define se second
#define no "NO\n"
#define yes "YES\n"
#define pb push_back
#define endl "\n"
#define pii pair<int,int>
#define pll pair<ll,ll>
#define dbg(x...) do{cout<<#x<<" -> ";err(x);}while (0)

void err() { cout << '\n'; }

template<class T, class... Ts>
void err(T arg, Ts... args) {
    cout << arg << ' ';
    err(args...);
}

const int N = 2e5 + 5;
const int M = 1e6 + 5;
const int inf = 0x3f3f3f3f;
const ll INF = 0x3f3f3f3f3f3f3f3f;
const int P = 1e9 + 7;
const double eps = 1e-8;
const double pi = acos(-1.0);

int n, m, s, t, mid, sqn, cnt, dep[N];
int tot=0, lnk[N], son[M<<1], nxt[M<<1];
bool vis[N];
vector<int>ans;

void add(int x, int y) {
    son[++tot] = y, nxt[tot] = lnk[x], lnk[x] = tot;
}

void dfs(int u) {
    dep[u] = 1;
        vis[u] = 1;
    for(int i = lnk[u]; i != -1; i = nxt[i]) {
        int v = son[i];
        if(vis[v]) continue;
        dfs(v);
        dep[u] = max(dep[u], dep[v]+1);
    }
    if(dep[u] == sqn) {
        ans.push_back(u);
        dep[u] = -1;
    }
}

void solve() {
    ans.clear();
    cin >> n >> m;
    sqn = sqrt(n-1)+1, tot=0;
    for(int i = 1; i <= n; i++)
        lnk[i] = -1, dep[i] = 0;
    for(int i = 1; i <= m; i++) {
        int x, y;
        cin >> x >> y;
        add(x, y); add(y, x);
    }

    if(n == 1) {
        printf("1\n1\n");
        return;
    }
    cnt=0;
    dfs(1);
    if(ans.size() == 0 || ans[ans.size()-1] != 1) {
        ans.push_back(1);
    }
    printf("%d\n", ans.size());
    for(auto i:ans) {
        printf("%d ", i);
    }
    printf("\n");
}

signed main() {
    IOS;
    int T = 1;
    cin >> T;
    while (T--) {
        solve();
    }
    return 0;
}
/*
1
15 14
1 2
2 3
3 4
4 5
5 6
6 7
7 8
8 9
9 10
10 11
11 12
12 13
13 14
14 15
15 16
16 17

2
4 3
1 2
2 3
3 4
6 7
1 2
2 3
3 1
1 4
4 5
5 6
6 4
*/