八年级上册英语一单元的所有单词和语法重点（单词表上的单词）。急用>O<

how often  多久一次 ； eg:  How often do you eat an Roujiamo?  How often does your sister’s mother lend you a book?   How often do your dogs bite a man?exercise  v.   锻炼；练习   eg