新手紧急求助：一道比较题

.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 microcomputer, four times as many than there were
(E) every thirty-two pupils now has one microcomputer, four times as many as

请教各位，这道题中“four times as many as"这个四倍指的是32个学生的数量，还是计算机的数量。另外，为什么前面用单数的“is",后面却用“were”。

哪位牛人帮忙解释一下，没人回答吗。。

there be结构的be由后面的单复数决定的，比较当中时态不同时，谓语不可以省略，这里前面now和后面four years ago,所以用is,were

非常感谢。但是后面为什么 用“were"呢，就是说前后比较的对象是什么。谢谢

还没有人回答吗？自己顶一下