Some scientists, who today are recognized for their brilliance, were

Responding to a pm:

It is an assumption question. It means you are looking for a gap between premises and conclusion. The premises are not enough to take you to the conclusion. You NEED the answer option to reach the conclusion. So the first thing we need to do is chalk out our premises and conclusion.

Premises:
Some scientists are recognized for their brilliance today.
They were once vilified for their work and considered insane during their lifetimes.

Conclusion:
What is considered insane or not insane has changed over time.

Now here is the catch. the premises say that some scientists were considered insane during their lifetime. They are being recognised as brilliant now. The premises do not say that they are not considered insane now - only that they are considered brilliant now. Note that we cannot assume that brilliance and insanity are mutually exclusive traits. Brilliant people can be considered insane too aka "mad scientists" .

To say that what is considered insane has changed over time, we are assuming that some of those scientists who were thought to be insane are not considered insane anymore.

Option (D) tells you this: Not all scientists who were once considered insane are still considered insane today.
So this is the correct answer.

All other options are just confusing or plain irrelevant.