The correct answer is option D.Understanding the passage1. Once their structures get published, naturally occurring chemicals (say, C) cannot be newly patented
2. NOC need to be out through the same rigorous testing program as any synthetic program before they can be used as a drug
3. This testing program results in a published report that details the chemical structure, effects, etc.
What this means: 1) To get cleared for use as a drug: C -> testing program -> published report (including structure) -> Cleared for use as a drug
2) Getting newly patented: C -> if structure gets published -> then C cannot be newly patented
Combining the above,
If C has been cleared for use as a drug, then
1. A report with its structure must have been published
2. Which means that it cannot be newly patented
(D) Once a naturally occurring compound has been approved for use as a drug, it can no longer be newly patented.
Option D is exactly what we arrived at
(A) Any naturally occurring chemical can be reproduced synthetically once its structure is known.We cannot infer this. We have no idea if knowing the structure equates to being able to reproduce the structure synthetically.
(B) Synthetically produced chemical compounds cannot be patented unless their chemical structures are made public.The passage only tells us that naturally occurring chemicals cannot be patented if their structures are published. We cannot be sure the same rule applies to synthetically produced chemical compounds. Maybe or maybe not. It is not necessary the same rules apply!
(C) If proven no less effective, naturally occurring chemicals are to be preferred to synthetic compounds for use in drugs.Effectiveness and preference are completely out of the scope of this passage, which is specifically about patenting and process to get approved for usage as a drug. How effective the chemicals are is beyond scope.
(E) A naturally occurring chemical cannot be patented unless its effectiveness as a drug has been rigorously established.Can be a confusing choice. But we need to remember - whether a naturally occurring chemical can be patented or not depends on whether its structure is published as per the passage. Nowhere in the passage do we see any indication that the effectiveness of the drug will influence its patenting.
This drug may be very effective or completely ineffective - it will not impact its patenting process.
Hope this helps.