sunglasses做主语时谓语动词用复数.如：
Where are my sunglasses?
They are on the table.
类似的还有glasses,trousers,compasses,pants等,但是当用a pair of/this pair of+这类词时,谓语动词用单数,如：
A pair of compasses is on the writing-table.
This pair of glasses is made in Shanghai.