题目

Jack reads a lot. He reads books in all of his free time. His brother Mike teases (取笑) him, because he thinks reading is boring, and he likes playing computer games. But their parents say reading is important. One day Jack reads a book about space (太空). He tells Mike about the interesting book. The very next week, Mike's science teacher gives his class some homework about space. They need to make a poster (海报) and a model about space. Mike is in a group with Liz, Anna and Jeff. They all think the homework is difficult. “My brother has a book about space,” says Mike. “Then let下列关于布朗运动的说法中正确的是A.布朗运动是固体分子的无规则运动B.悬浮微粒做布朗运动，是液体分子的无规则运动撞击造成的C.液体温度越低，布朗运动越剧烈D.悬浮微粒越大，液体分子撞击作用的不平衡性表现得越明显