GMAT Critical Reasoning (CR) | Re: Various forms of plant and animal life have longer life spans than Hom

I think answer is D. Please correct me if below reasoning is wrong.

Boil down version - Because some plants and animals live much longer than humans, scientists can study their complete life-cycle by observing many specimens at various stages.
This principle also applies to astrology or geology. Scientists can observing various specimens.


A) Methods of observation are the same for most subjects. - Even if method of observation is different, argument still holds as it only talks about observing
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