Look at the lost and found case.What's that?It's[ ]book.A the B a

Look at the lost and found case.What's that?It's[ ]book.A the B a
我要听分析，懂了才好，月考就不会错这个了.我补充一句。这两句不是对话，是同一个人说的，我只是省略了下文。