根据短文内容，选词填空。

Lu Ban was a craftsman. One day a leaf (A: cut / B: cuts) his finger. He looked at the leaf. (A: careful / B: carefully). There were many (A: tooth / B: teeth) on the leaf and they were sharp. So he made a tool with teeth like (A: these / B:this). It could cut things. It was a saw. It was the first saw in the world. People are still (A: use / B: using) this tool today.