A.yes,後面当然是要跟 it is 啦.
B.没错.
C,D.Yes,this is 和 No,this isn't 句子结构不完整.
你的小孩学过Tag Questions (例如是 he is; she doesn't; they will,we could; it isn't; I can 等等)
This 跟 he she it 等 pronouns 在 tag questions 里的应用不同,应用在 S+V+O / S+V+C 的基本结构懂吧?This is my coat; this is mine; this is not my coat 就没有问题了.回答 yes no question 想用 this 的话就必须使用完整句子.