Answer: C would be the best answer
Step-by-step explanation:
choice c,d,e can be tested although d and e are incorrect hypotheses whereas c is correct.
obviously choices a and b cannot be tested because there’s no experiment to determine wether or not an organism was the “first” to do something.
Then again all hypotheses except c are incorrect.
snails weren’t the first. Cynobacteria were the first not plants. We need both producers(autotroph plants) and consumer(heterotrophs) in a functional system and the co2 made and o2 used by heterotrophs has to be compensated for by the o2 made and co2 used in autotrophs. Elodea plants both consume and produce co2.