def toDykta(A):
    dick = {}
    for i in range(len(A)):
        if A[i] not in dick:
            dick[A[i]] = [i]
        else:
            dick[A[i]].append(i)
    return dick

def test():
    n = int(input().strip())
    Asc = [set() for i in range(n)]
    XValues = [1 for i in range(n)]
    visited = [False for i in range(n)]
    Father = [None for i in range(n)]
    LeavesBelow = [0 for i in range(n)]

    for i in range(n-1):
        a,b = input().split(' ')
        a = int(a)-1
        b = int(b)-1
        Asc[a].add(b)
        Asc[b].add(a)

    dfs(0, Asc, XValues, visited,Father)
    for starting_point in range(n):
        if (XValues[starting_point] == 1):
            vertus = starting_point
            while (vertus != None):
#                print('Incrementing', vertus, 'leaves count')
                LeavesBelow[vertus] += 1
                vertus = Father[vertus]

    Xdick = toDykta(XValues)
#    print(Xdick)
    returns = []
    for dval in Xdick:
        if(sum([LeavesBelow[qq] for qq in Xdick[dval]])==LeavesBelow[0]):
            returns.append(dval)
    print(len(returns))
    returns.sort()
    for r in returns:
        print(r, end=' ')


def dfs(starting_point, Asc, XValues, visited,Father):
    visited[starting_point] = True
    for vert in Asc[starting_point]:
        if( not visited[vert]):
            dfs(vert, Asc, XValues, visited,Father)
            Father[vert] = starting_point
            XValues[starting_point]+=XValues[vert]



Z = int(input().strip())
for i in range(Z):
    test()