more than doubled直接能作谓语吗？

987-791.        The number of undergraduate degrees in engineering awarded by colleges and universities in the United States increased by more than twice from 1978 to 1985.

(A) increased by more than twice

(B) increased more than two times

(C) more than doubled

(D) was more than doubled

(E) had more than doubled

正确答案是C.　（OG72中也是这样）

但我的困惑是：用了C后，整个句子的谓语是谁呢？难道主谓变成了 number more than doubled？

潜意识中，总觉得more than前面要有个系动词或者其他的动词吧，太别扭了。

百思不得其解啊，盼NN解答，不胜感激！

赞成，double本身可以做动词

其他选项都不符合习惯用法

如果没有more than，　我认为这样是完全正常的。

但是有了more than以后，就奇怪了，莫非做doubled的状语吗？老大能否举个例子呢。

我从没有见过这种用法，困惑中。。

是more than作副词修饰动词double的用法吧

我去网上查了一下外国人的新闻，发现这种用法外国人常用，也许只是我不知道而已。

就算是长个见识吧：

1: Google's profits more than
            doubled in the second quarter, as the company continued to increase its share of the lucrative search advertising market.

2: Perinatal mortality in Iraq more than tripled since sanctions.