情景交际：根据上下文补全对话。

A: Mum, 1_____ is my cap? I can't 2_____ it. 3_____ you know?

B: 4_____ 5_____ on the bed?

A: No, 6_____ 7_____.

B: Is it behind the chair?

A: 8_____. Oh, I'm late today. It's time for class.

B: Don't worry, dear. Look! It's 9_____ your head!

A: Thank you very much, Mum! 10_____.

B: Bye!

下列哪项是缺铁性贫血最常见的病因（）

A.慢性胃炎

B.慢性肝炎

C.慢性溶血

D.慢性感染

E.慢性失血