例句：
The mayor of Beijing said that all construction work for the Beijing Olympics had been completed by the year 2006 .
考查时态的用法：时间是：by the year 2006，by+过去时间，要用过去完成时。
by (the end of) last year（by+过去时间）; two days before（一段时间+before）; for和since说明的时间同时用于句中;by the time + 从句（过去时态）等时间状语时，谓语动词用过去完成时
