专题六 状语从句 ◆时间状语从句的考查要点 1.before引导的从句中不用否定式谓语。常用如下句型: it will be long before...(得过好久才……) it will not be long before...(过不了多久就……) it was long before... (过了好久才……) it was not long before... (过了不久就……) 2.since后面所用动词不同,该动词所表示动作持续时间的计算方法也不同。 since+瞬间动词过去式从该动作发生时算起since+持续性动词过去式从动作结束时算起 it is two years since he joined the army.他参军两年了。