新概念的问题:单复数\时态新概念第三册:中有一句话:peoplewhoworkinofficesarefrequentlyreferredtoaswhite-collarworkersforthesimplereasonthattheyusuallywear(acollarandtie)togotowork.这里为什么用acoll

Question

新概念的问题:单复数\时态
新概念第三册:中有一句话:people who work in offices are frequently referred to as white-collar workers for the simple reason that they usually wear (a collar and tie) to go to work.这里为什么用a collar and tie 而不用collars and ties?
an american team explored a temple which (stands) in an ancient city on the promontory of ayia irini.这里stands 为什么不用stood?
回复sgdgzsg 同一段：they had large rooms with beautifully decorated walls.这个也是一直在那,为什么就不用一般时?

Answer 1

我感觉they是虚指,不是复数的概念.我原来老爱用he or she如何如何,我的英语老师（洋人）就告诉我,我们都用they如何如何,不用he or she.
它一直在那,一般时
mother's day中mother是指群体,所以不是mothers'
第二个：我认为temple是直到探险队发现它的时候还在stand那,但是large room那个还是直到探险队发现时还是完好如初的吗?我猜是不是这个原因