答案：B
解析：Jenny's brother's been at this school for over two years.这个句子是现在完成时,其结构：has + 过去分词been,所以Jenny's brother's 是 Jenny 's brother has 的缩写
反义疑问句：前肯,后否,所以用：hasn't he?
不明白的再问哟,请及时采纳,多谢!