请英语大神帮忙看看我这句错在哪,怎么改?

问题描述:

请英语大神帮忙看看我这句错在哪,怎么改?
Imagining that you sit in your room,all around you were .(主要问题在imagine引出想像情景的用法及在想像情景中是否用虚拟语气),

首先 ,祈使句 imagine应用原型,that从句接状态,所以应该是you sitting in your room.整个句子就是 imagine you sitting in your room,all around you were .为什么all around you后还用were?