问题补充：
They got two free tickets to Canada, otherwise they able to afford to go.
A. wouldn’t have been
B. mustn’t have been
C. wouldn’t be
D. hadn’t been
答案：
(答案→)A. wouldn’t have been
B. mustn’t have been
C. wouldn’t be
D. hadn’t been
解析：句意：他们得到了两张去加拿大的免费票，否则他们是绝对出不起旅费的。否则；要不然，后面用would have done表示与过去事实相反的虚拟语气，本句相当于：If they hadn’t got two free tickets to Canada, they would, they wouldn’t have been to afford to go.
