长牙会很难受，婴儿会烦躁不安。Teething can be painful and make your baby irritable.我的小弟弟直发脾气,因为正在长牙.My brother is fretful because he is cutting his teeth.很多婴儿到一岁大时才开始长牙。Many infants do not cut their first tooth until they are a year ol...
The two principal combustion products are water vapor and carbon dioxide.两种主要的燃烧产物是水蒸气和二氧化碳。The car windows were fogged with vapor.车窗上满是雾气。When nitric acid is poured on copper, a brown vapor gives off.将硝酸倒在铜上, 会散发出一种棕色的蒸...