Unit 7 Its a dog.习题习题 21、单项选择。单项选择。1. - Moo, moo! Whats it?- Its a _.A. dog B. cow C. duck2. - Quack, quack! Whats it?- Its a _.A. dog B. cow C. duck3. - Squeak, squeak! Whats it?- Its a _.A. duck B. cow C. mouse2、翻译下列句子。翻译下列句子。1. Is it a cat? 2. No, it is not a duck.