说说下列句子的意思：

—Why don't you get a watch for your friend as a gift?

—But it's too expensive for me _______!

阅读短文，下列问题

A

    My name is Joe. I'm a student in No. 1 Middle School. I have a brother and a sister. They are Tony and Mary. We are in different schools. Every morning, we get up at half past six. At seven o'clock, we have breakfast with our parents. Then we go to school.

    Tony's school is about two kilometers from our home, so he goes to school by bike. He thinks it's healthy. It takes him about ten minutes to get to school. Mary is in No. 3 Middle School. How does she go to school? She takes a bus first. Then she has to take the subway. She needs forty minutes to get to school every day.

    I walk to school because my school is only one kilometer from my home. I need about ten minutes to get to school. And I'm never late for school.

自然界中的物体可以分为两类：一类是____，一类是____。