Ⅰ.核心单词→识记·思考·运用
一、单词拼写
1．(2015·湖北，阅读D) Without gravity to help ________(循环)air，the carbon dioxide you exhale has a tendency to form an invisible cloud around your head.
2．She is continually ________(滥用)her position by getting other people to do things for her.
3．The ________(根本的) cause of his success is his hard work.
