语法与词汇 15.The old rules have to be ______because they only applied to the circumstances that existed when they were made a hundred years ago.
【正确答案】 D
【答案解析】句意：旧法规必须重新修订，因为它们只适用于100年前立法时的情况。A项意为“发展”；B项意为“建立”；C项意为“观察”；D项意为“修改”。只有D项符合题意，答案选D。