need 有兩個(gè)作用,一個(gè)是情態(tài)動(dòng)詞,另一個(gè)是及物動(dòng)詞.
翻譯成“必要”的時(shí)候是情態(tài)動(dòng)詞,和其它的情態(tài)動(dòng)詞一樣,后面接動(dòng)詞原形,可以幫助構(gòu)成疑問和否定；如 you needn't tell me that.
翻譯成“需要”時(shí)是及物動(dòng)詞,后面要接賓語(yǔ).
如 I need your help.
如果說你舉的例子有問題,可能是語(yǔ)義方面,而不是語(yǔ)法方面.
must you play the piano at such a late hour?似乎更合理一些：你非得這么晚彈琴嗎?
淺見,僅供參考.這是原題：John，look at the time._____you paly the piano at such a later hour?A.Must B.Can CMay D.Need.選A約翰，看看幾點(diǎn)了？你非得這么晚彈鋼琴嗎？