I originally thought of this as a quant problem: if it's "within weeks," then it must be less than or equal to multiple weeks; so it could be less than 2 weeks and therefore be 1 week which would NOT be several.

BUT, I think the "within" is used more here to signify "surprise" that it only took several weeks. It could have said "And in ONLY several weeks, ... something was made that reproduced the conditions billions of years ago..." But that is too wordy, so in English, we say "within" instead of "only several weeks."

If we said "the hotel was constructed within days" there's no way it was built in one day, the author would just put emphasis that it wasn't constructed in MONTHS.

That's how I'm justifying it at least.

The answer is C and correct i guess

If one is thinking why it is not B
then it is said that further experiments lead to discovery in B not that specific one in 1953

others are no related to experiments in 1953

My answer -D

C