目标 1.learn the useful words and expressions in this whole unit: astronomy system theory billion globe violent atmosphere unlike harmful chain multiply exist puzzle biology crash pull float mass solar system, in time, lay eggs, give birth to, in one’s turn, prevent…from, cheer up, now that, 2. study the pronunciation of the key words. 3. preview the whole unit. 重点 to get familiar with the pronunciation and meaning of the key words and expressions 二次备课
