Supermarkets are large self-service stores selling every kind of food fresh,canned or frozen.
问题描述：
Supermarkets are large self-service stores selling every kind of food fresh,canned or frozen.
请问：Supermarkets are large self-service stores是个完整的句子,后面再跟selling every kind of food fresh,canned or frozen.
它是什么结构
答
后面跟的selling……是对stores的进一步说明,作补语