Is that being a dog.中为什么is和being会同时出现?

Is that being a dog.中为什么is和being会同时出现? that a dog is a dog is being petted adog being petteda dog is being petted a dog being petted 区别不同 That is a dog .改为否定句 That girl is a lucky dog W( ) is that girl with a dog Is that being a cat中为什么要用being That [are/is] a dog.是 is 还是are? 中文意思：you have a dog.is that your dog?no,it is yours. what a love dog!Is that her dog?_________________快！我急用啊！ What a lovely dog!Is that her dog?No,__________._______________________._______________.Are these What's that behind the door?A.It is a little dog.B.Yes,it is a little dog.C.There is a little dog near the door is that a dog in the garden?i can not find out ____ it is a dog or a cat it is a dog It is a dog. It is ( ) a dog? Is that your dog?What is name? What's this?___ A This is a dog B That's C It's a dog D I'm a dog明天交的,