what color are their hair?hair加不加s

what color are their hair?hair加不加s what color is their hair还是what color are their hair what's the _____ of their hair? what color is your hair的回答 ----What color _____ your hair?----Black. What is the _____ ______ their hair? What color is her hair 用英语回答 dye one's hair blue和 color on'e hair blue有什么区别? what color----her hair and what color---her eyes 句中应该怎样用'is' what's the ___ of theit hair? What's this?It's___(hair) hair