He had to walk upstairs as the lift was out of order.
当电梯坏了 和 因为电梯坏了 都说得通,遇见这种该怎么样分辨呢?
判断as 引导的是“时间”还是“缘由”从句，告诉网友一个技巧：
1. 当as 从句的谓语动词表示状况时，一般是“缘由从句”。
He had to walk upstairs as the lift was out of order.
was out of order：是“系表结构”表状况。所以是“缘由从句”。又如：
As he is a troublemaker, no one likes to work together with him. 由于他这个人爱惹是生非，大家都不愿同他共事。
2. as 表示时间时，主、从句中的两个动作一都是延续性的，而且都是同时进行的，意为“一边...一边...；伴随...”。比如：
But as time passed, I grew bored with an idle lifestyle.
不过，伴随时光消逝，我日渐厌倦了清闲的生活方法。
She sang as she walked.
她边走边唱歌。
