问题补充：
When I got on the bus, I I had left my wallet at home.
A. was realizing
B. realized
C. have realized
D. would realize
答案：
A. was realizing
(答案→)B. realized
C. have realized
D. would realize
解析：考察时态，根据when I got on the bus可知,此处时态选择的是一般过去时,句意为,当我上车的时候,我意识到了我把钱包忘在家里了.
