One evening when it was swarm, I stayed awake until half past eleven in order to have a good look at the moon by myself.
A. on average
B. on purpose
C. on sale
D. on schedule
网友回答
A. on average
(答案→)B. on purpose
C. on sale
D. on schedule
解析：on average通常，平均；on purpose有目的地；on sale廉价出售；on schedule按时。句意：一天晚上我一直故意没有去睡觉，直到晚上11:30，为了自己去看看月亮。根据句意故选B。