come up 和come about都表示发生时有什么区别?

come up与come about皆有“发生”之意,且都为不及物动词,且后者多作不可避免之意,多用于疑问句,而come up本义为“occur,arise出现/发生”,如：We'll let you know if any vacancies come up。一有空缺我们就通知你。I shall write to you if anything comes up。如果发生了什么事情我将写信告诉你。Can you tell me how the accidents come about?你能告诉我事故是怎样发生的吗?再者,这两个单词在中文里都有“发生”的意思,我们无法区分的话就只能看原来的英文解释了,呵呵(⊙o⊙)!come up v。1。bring forth,usually something desirable 2。result or issue 3。move toward,travel toward something or somebody or approach something or somebody 4。come to the surface 5。originate or come into being 6。move upward 7。be mentioned 8。start running,functioning,or operating 9。get something or somebody for a specific purpose 10。come up,of celestial bodies11。gather (money or other resources) together over time12。gather or bring together come about v。come to pass 比如：How did the accident come about?这个事故是怎么发生的?