coverit

import sys
import os
if not os.environ.get("ONLINE_JUDGE"):
    sys.stdin = open('./in.txt', 'r')
    sys.stdout = open('./out.txt', 'w')

for _ in range(int(input())):
    n,m =map(int,input().split())
    odd_nodes = []
    even_nodes = []
    al = [[] for _ in range(n+1)]
    visited = [False]*(n+1)
    level = [sys.maxsize]*(n+1)
    for _ in range(m):
        u,v = map(int,input().split())
        al[u].append([v,0])
        al[v].append([u,0])

    # print(*al)
    queue = [1]
    level[1] = 0
    even_nodes.append(1)

    visited[1] = True

    while queue:
        u = queue[0]
        queue.pop(0)

        for edges in al[u]:
            v,w = edges
            if not visited[v]:
                visited[v] = True
                queue.append(v)
                level[v] = level[u]+1

                if level[v] %2 == 0:
                    even_nodes.append(v)
                else:
                    odd_nodes.append(v)

    if len(even_nodes) > len(odd_nodes):
        print(len(odd_nodes))
        print(*odd_nodes)
    else:
        print(len(even_nodes))
        print(*even_nodes)