Harry is a curious (好奇的) boy. He likes asking questions. So, when Harry saw a tree next to the gate, he asked his dad, "What is that tree made of?"
Dad gave his answer, "Wood … branches (树枝) … leaves."
"What's that rock over there made of?"
"Rock," Dad answered quickly.
"How about the car? What is it made of?" Harry asked again.
Dad thought for a moment and answered, "Plastic, metal, and glass mostly, and maybe some rubber."
"How about the air?"
"It's made of air. Scientists have found many kinds of air and mixtures (混合物) of those kinds of air. Everything is made of stuff. It is like Mom's pantry (食品储藏室), but we're not baking bread or cookies here. We're making stuff. There are about 100 ingredients (成分) called elements (元素) to make everything, but most things have only a few of them."
"Even me?" Harry asked in surprise.
"Yes, you're mostly carbon, hydrogen, nitrogen, and oxygen, but there are other elements in you. Each piece is so small that we can't even see it."
Harry was happy about his father's answers. And dad continued reading his newspaper, only to be interrupted a few minutes later with another question, "And the trees then?"
