Ten houses had been built by them by the end of last year這是過去完成時態(tài)嗎？對，確切的說時過去完成時態(tài)的被動語態(tài)。had后面不加not嗎？原句是肯定句，轉(zhuǎn)換成被動語態(tài)后仍然是肯定句那改成問句呢？Had they built ten houses by the end of last year?had提前就行原句中有already是不是就變否定句？不是啊，already只是一個程度副詞，沒有否定含義。