问一个英语填空问题?

题目

问一个英语填空问题?
A:where ____ your sunglasses?（可以填 are 吗))
B:_____ on the table
A:NO ___ not,They are my sunglasses!
B:You are right!My sunglasses ____ in my purse!
我知道是用 is 和 are 填空,请说明为什么那么填

答案

are
they are
they are
are
像这种成对出现的词没有量词（a pair of)就用复数