When he fell off the bike, he tried but couldn't .
A. to have stood up
B. standing up
C. to stand up
D. having stood up
网友回答
A. to have stood up
B. standing up
(答案→)C. to stand up
D. having stood up
解析：fall off the bike意为: 从自行车上跌下来,try to do sth.意为：尽力做某事。