你可以把often放在句首,这样就容易理解了.这里的often修饰这个句子,做状语.
------- （Very）often,it is the case that / when - - - - - .你的说法靠谱，但是比如都是频度副词的twice a year、once a week与often the case差不多，那么：Twice，he go shopping a week这种句子貌似没见过-_-|呵呵， twice a week是个短语，不能分割，不过你可以把这个短语放在句子开头，照样达到同样的效果。那么就是说类似often这样的副词都可以在主系表这种结构的句子中做单独的状语吗？能帮我再举个例子吗，最好是放在句子里的，不要句首的^_^1 She's always too busy working to look after her family members.
== Always is she too - - -- -.
2 They are never pleased with her work.
== Never are they pleased -- - -
3 He's sometimes seen to play football in the street.
== Sometimes he's seen - - - -