it won't be very long before + 句子（谓语动词用一般现在时）如：It won't be long before I return to Beijing翻译：我很快就要回北京了It will be two weeks before she comes here.翻译：过两周她就来了.How lo...此否定结构能否把before 换为until?你好。不可以，因为它们之间不存在互换关系。 It won't be long before I return to Beijing------It won't be long until I return to Beijing.(是错句)，但这一句是对的：I won't return to Beijing until Monday / -- ---until next week./ -- -- - until five days from today.