A:④⑤、①②③、⑥
B:②③⑥、④⑤、①
C:⑤⑥、①②③、④
D:①④⑤、②⑥、③
①资本积累 ②工业原料 ③商品市场 ④黑人奴隶
We must ___________ ourselves ___________ our work.