英语变复数句the要不要去掉例题 is the boy your friend?

英语变复数句the要不要去掉例题 is the boy your friend? 有这么一句英语句子：海豚是濒危动物.请问海豚这个词前面要不要加The?海豚这个词要不要变复数? 请问That is her brother.变复数句,要不要把her变成their啊? My favorite fruit is orange orange要不要变复数 the dog is big.(变复数句） this is knife in the box（变复数句 There is an apple in the box.变复数句 This baby is sleeping on the train变复数句 he is listening to the teacher.变复数句 The basketball game is in November. 变复数句,谢谢 A photo is in the drawer.（变复数句） The dictionary is mine.变成复数句?The dictionaries are mine.有时都变复数，有时只是一部分变复数，到底什么时候该变什么时候不变？ 英语单数句变复数句 what's the price of中的be可以使用复数形式吗?还有price要不要变复数? She is my friend.变复数句 she is an airhostess.变复数句 this.is pen变复数句 Is your case?变复数句