急需！！！解答一題英文填空！！！Please！！！?

［答案］sit back
［文法］All I need/ want /have to do is do sth
這是固定結構，意為"我只需要/想要/必要去做的是…"
［例證］
歌曲名：All I wanna do is love your body （Chirstina Anguilera ）
歌曲名：All I wanna do is be with you.（ Paul Weller）
歌曲名：All I want to do is make love to you（heart）
歌詞：All I wanna do is find a way back into love.
我只想要重新找回愛（Way back into love）

(請不要匿名發問)
All Fiona wants now is _____ _____(sit back) in her own armchair, listening to the soft music.
原句須填不定詞 to sit back，is to +V 表示想做但尚未，這才符合句意want

如果你用 is sitting back 表示她正坐在椅上
All Finoa enjoys now is stting back in her own armchair...


如果原句加上 to do
All Fiona wants to do now is 則用原型 sit back 或 to sit back 都可以
這是一個特殊的句型，背下一個例句 All I want to do is dream.
該句型is後接原型是標準的型式，有些人不習慣則採用不定詞 to+原型V
All I want to do is sleep.
All I want to do is have some fun.

[補充]
看一下這解說，同一句子
https://tw.answers.yahoo.com/question/index?qid=20120906000010KK00555

If anyone needs more evidences, check these out
http://english.stackexchange.com/questions/115659/is-this-sentence-right-correct-what-i-want-to-do-is-read-this-book
http://english.stackexchange.com/questions/122277/omitting-the-last-to-in-all-i-need-to-have-to-must-do-is-to-do-somet
http://english.stackexchange.com/questions/104546/all-you-have-to-do-is-read-vs-all-you-have-to-do-is-to-read

填「動名詞片語」：sitting back
當作「主詞補語」，因為主要動詞是「連繫動詞」is