Potatoes is my favorite food .中的系动词是is么?

My favorite food ( ) potatoes.是用is还是are 为什么? my favorite food is hamburgers为什么be动词用is? my favorite food is noodles.food用单数还是复数?系动词用单数复 my favourite food is potato还是potatoes? My favourite food is potatoes.对potatoes提问,怎样提? My favorite food is cakes my favorite food is ____. my favorite food is hamburgers. my favorite food is noodles. 英语手术台：是My favorite food is fish and tofu.还是My favorite food 是My favorite food is green beans.还是My favorite food are gree My favourite food is tomatoes and potatoes对吗?