问题补充：
--- Jack fell off the ladder yesterday, but he is all right now.
---What a lucky dog! He himself badly.
A. should injure
B. could have injured
C. should have injured
D. might injure
答案：
A. should injure
(答案→)B. could have injured
C. should have injured
D. might injure
解析：句意：——昨天杰克从自行车上掉下来了，但现在没事了。——真幸运！他可能会受伤的。由语境可知，空格处表示对过去情况的推测，应该在BC里面选择，could have done 意为“可能会…却没有”；should have done 意为“过去应该干某事而没有干”。故B项正确，
