求解释

In 2000, a mere two dozen products accounted for half the increase in spending on prescription drugs, a phenomenon that is explained not just because of more expensive drugs but by the fact that doctors are writing many more prescriptions for higher-cost drugs.

1. a phenomenon that is explained not just because of more expensive drugs but by the fact that doctors are writing
2. a phenomenon that is explained not just by the fact that drugs are becoming more expensive but also by the fact that doctors are writing
3. a phenomenon occurring not just because of drugs that are becoming more expensive but because of doctors having also written
4. which occurred not just because drugs are becoming more expensive but doctors are also writing
5. which occurred not just because of more expensive drugs but because doctors have also written

怎么成了全画线了

以下为个人观点:

答案是D

解释:在2000年，有24种药物（产品）占了该年度所增加的处方药物花费的一半，这种现象之所以发生，不仅是因为药物价格越来越高，还是因为医生正在更多地开的高价药物处方。

A的错误在于:1、not just ...but also ...所连接的项目不对称.2、explained (not just) because of是不对的。后面的by the fact可以。因为这里是被动语态，be explain by sth可以，而be explained because of则行不通。

B的错误在于：（当然，Ｂ完全有可能是对的）后面的fact可以省略，毕竟只是简单的重复。

C的错误在于：not just ...but also ...所连接的项目不对称.前面是fact，后面是短语。

E的错误在于：同A。

我一个同事认为答案是Ｂ，说Ｄ的also不应该和but分开。ｌｚ自己对照正确答案分析好了。