化学在生产、生活等领域都有着广泛的用途．请回答下列问题：

Martin: What do you want to be when you grow up, Jiamin?

Jiamin: I want to be a fireman (消防员). I think the fireman is cool.

Martin: And you, Lily?

Lily: I like children. I want to be a teacher. What about you, Martin?

Martin: My father is a police officer. He can stop bad people. So I want to be a police officer.

Jiamin: Police officer can help people. Your father is great, Martin.

Martin: Thanks. Look, Miss Wang is hard-working. I think the teacher is great, too.

郑人买履

    郑人有且置履者，先自度其尺而置之其坐。至之市而忘操之。已得履，乃曰：“吾忘持度。”反归取之。及反，市罢，遂不得履。人曰：“何不试之以足？”曰：“宁信度，无自信也。”