(三)when和while的区别还在于:while引导的时间状语从句多用进行时态，而when引导的时间状语从句多用一般时态。如：Whiletheyweretalking,thebellrang.他们谈话的时候，上课铃响了。Iwasdoingmyhomeworkwhenmymothercamebackhomeyesterdayevening.昨天晚上妈妈回家的时候，我正在做家庭作。[链接]as所表示的动作与主句同时发生...
Health and environment officials have collected water samples from the Mekong River at Khut Khu rapids in Chiang Kan district of Loei province for testing, after sulfuric acid leaked into the river from a truck which overturned in Luang Prabang yesterday. Laotian officials had issued an announcement...