在七年級(jí)時(shí),大家學(xué)習(xí)了always,usually,often,sometimes,never等表示時(shí)間頻度的副詞.這些詞通常用來說明在一段時(shí)間內(nèi)做某事的多少或某種狀態(tài)存在的次數(shù)的多少.例如：
We usually get up at half past six.我們通常六點(diǎn)半起床.
Sometimes he goes to see his grandpa on weekends.周末,他有時(shí)候去看望爺爺.
但是,在日常生活中,我們不可能總是用陳述句來表達(dá)自己的或他人的一些行動(dòng),或者事物所存在的狀態(tài).我們還要向?qū)Ψ教岢鲆恍﹩栴},請(qǐng)求對(duì)方回答.在這種情況下,我們還要用疑問句.請(qǐng)看下面幾組對(duì)話：
1.—How often do you play football?
—I usually play football after school.
2.—How often does Mary go to the concert?
—She often goes to it on Saturday evening.
3.—How often does my daughter take the medicine?
—Three times a day.
不知大家是否注意到,我們針對(duì)上面所說的頻度副詞和表示“在某段時(shí)間內(nèi)某種動(dòng)作的次數(shù)”的狀語提問時(shí),都要用how often.換句話說,如果要回答由how often提問的句子,我們通常要用頻度副詞或諸如every day,each week,once a week,twice a day,four times a month等來回答.例如：
4.—How often do you borrow books from the library?
—Twice a month.
5.—How often does your mother do the washing?
—She does it every day.
6.—How often can you go to the movie?
—Once a week.
在大家所做的練習(xí)中,常見的有“句型轉(zhuǎn)換”.這種題型有一種“就劃線部分提問”,要求針對(duì)陳述句中的劃線部分提出問題（也就是把陳述句變成特殊疑問句）,其中就有針對(duì)上面所說的頻度副詞或every day,each week,once a week,twice a day,four times a month等提問的句子.這時(shí)候自然要用how often來提問了.例如：
Jack watches TV three times a week.→How often does Jack watch TV?
Our school has a sports meeting twice a year.→How often does your school have a sports meeting?
要注意的是,陳述句在變成這種特殊疑問句時(shí),其結(jié)構(gòu)是：How often+助動(dòng)詞（或系動(dòng)詞 be）+主語+實(shí)義動(dòng)詞（如果前面是系動(dòng)詞be的某種形式,則不再用實(shí)義動(dòng)詞）+其它成分?