have to be是什么時(shí)態(tài)

　　You have to be careful what you say on TV.

　　在電視上說(shuō)話(huà)時(shí)你不得不謹(jǐn)慎。

　　Bathrooms don't have to be purely functional.

　　浴室不必完全只為了實(shí)用。

　　Premature babies have to be fed intravenously.

　　早產(chǎn)兒必須通過(guò)靜脈輸入來(lái)喂食。