RT

#include<bits/stdc++.h>
using namespace std;
const int MAXN = 2e5+10;
const int MAXM = MAXN << 1;

int n, m;

struct Node {
	int u, v, next;
} edge[MAXM];
int head[MAXM], cnt;

bool vis[MAXN];
int pre[MAXN];
int newpos[MAXN];
int now, ans;

void add(int u, int v) {
	edge[cnt].u = u;
	edge[cnt].v = v;
	edge[cnt].next = head[u];
	head[u] = cnt++;
} 

void adde(int u, int v) {
	add(u, v);
	add(v, u);
} 

void DFS(int u) {
	newpos[now++] = u;
	for(int i = head[u]; ~i; i = edge[i].next) {//按位非 
		int v = edge[i].v;
		if(vis[v]) {
			continue;
		}
		vis[v] = true;
		pre[v] = u;
		DFS(v);
	}
}

bool cover[MAXN], res[MAXN];

void MDS() {
	for(int i = 0; i <= m; i++) {
		cover[i] = 0;
		res[i] = 0;
	}
	for(int i = n - 1; i >= 0; i--) {
		int t = newpos[i];
		if(cover[t]) {
			continue;
		}
		if(!res[pre[t]]) {
			res[pre[t]] = true;
			ans++;
		}
		cover[t] = true;
		cover[pre[t]] = true;
		cover[pre[pre[t]]] = true;
	}
	int cnt = 0;
	printf("%d\n", ans);
	for(int i = 1; i <= n; i++) {
	    if(res[i]) {
	        cnt++;
	        printf("%d ",i);
	    }
	}
	printf("\n");
}
void init() {
	cnt = 0;
	for(int i = 0; i <= m; i++) {
		head[i] = -1;
		vis[i] = 0;
		pre[i] = 0;
		newpos[i] = 0;
	}
}
int main() {
    int T;
    scanf("%d", &T);
    while(T--) {
        init();
    	scanf("%d%d", &n, &m);
    	int u, v;
    	for(int i = 1; i <= m; i++) {
    		scanf("%d%d", &u, &v);
    		adde(u, v);
    	}
    	ans = 0;
    	now = 0;
    	vis[1] = true;
    	pre[1] = 1;
    	DFS(1);
    	MDS();
    }
	
 	return 0;
}