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不容易有的机会；极小的可能性
?极罕见的机会
... 罕见的疾病 rare disease 极罕见的机会 offchance 极为罕见的 extremely rare ...
You remember when you were little and you would keep checking the sky for snow clouds on the offchance that you got a snow day?
FORBES: IRS Won't Delay Tax Season For Sequestration
英汉双解词典包含3185865条英汉词条，基本涵盖了全部常用单词的翻译及用法，是英语学习的有利工具。