1.原句 ：The books are on (aren't) the bookcase .
否定句 ：The books are not (aren't) on the bookcase .
(我觉得你题目上的单词" book" 应该是单词"books" ,因为你在后面用了"are"一词.而单词"are"是一个用于复数形式的单词）
2.原句 ：The baseball is under the bed.
一般疑问句 ：Is the baseball is under the bed .