一道死活想不通的题目

Naturally occurring chemicals cannot be newly patented once their structures have been published. Before  a naturally occurring chemical compound can be used as a drug, however, it must be put through the same rigorous testing program as any synthetic compound,cuminating in a published report detailing the chemical's structure and observed effects.

if the statement above are true, which of the following must be also true on the basis of them ?

A,B,C很好排除，关键是D和E

D)once a naturally occurring compound has been approved for use as a drug, it can no longer be newly patented.

E)a naturally occurring chemical cannot be patented unless its effectiveness as a drug has been rigorously established

答案选D,我觉得E更合适，为什么选D呢？ 

a naturally occuring compound被approve为drug的前提是它的structure在published report中出现，而根据第一句，一旦被publish过，就不能再newly patented.

觉得infer题里常常会出现矛盾的两个问题，然后结论是二者不可兼容。