天气的种类: thunderstorm, hailstorm, tornado, sandstorm.blizzard.monsoon,humncane 风暴的组成部分: sand grain, snowflake crystal, raindrop, hail pelet 数词的用法，例如:billion,trillion 介词的用法，例如:in,on, over, into 连词的用法，例如:and,so,until 情态动词的用法，例如:can 并列句，例如: Weather cools and heats our planet so it is just rightfor life. 定语从句，例如: Monsoons are winds that change each season. 特殊疑问句，例如:What's happening?