89. A recent national study of the public schools shows that there are now one microcomputer for every thirty-two pupils, four times as many than there were four years ago.

(A) there are now one microcomputer for every thirty-two pupils, four times as many than there were
(B) there is now one microcomputer for every thirty-two pupils, four times as many than there were
(C) there is now one microcomputer for every thirty-two pupils, four times as many as there were
(D) every thirty-two pupils now have one micro¬computer, four times as many than there were
(E) every thirty-two pupils now has one microcom¬puter, four times as many as

答案是D，但是后半句为什么用there were呢？ 前面用的是单数形式啊～～～是因为有four times吗？但是four times 是用来修饰后面的there were的吧，想不通是为什么。哪个nn可以指点一下哈，先谢了.