问题补充：
Jack described his father，who a brave boy many years ago，as a strong－willed man.
A. would be
B. would have been
C. must be
D. must have been
答案：
A. would be
B. would have been
C. must be
(答案→)D. must have been
解析：根据语境可知，此处表示的是对过去事实的推测，所以用must have done结构。注意句中有一个非限制性定语从句将主句分隔开了。
