Question

select the correct answer.
which compound was abundant in precambrian earths oceans, before complex life evolved on earth?
a. dissolved oxygen
b. dissolved carbon dioxide
c. dissolved methane
d. dissolved ammonia

Explanation:

Before complex life evolved (like plants that produce oxygen via photosynthesis), the atmosphere and oceans had high levels of carbon - based compounds. Methane is a simple carbon - containing compound. Dissolved oxygen would increase after the evolution of photosynthetic organisms. Ammonia was not as abundant as methane in this context. Carbon dioxide is a gas, but methane (as a compound) was more relevant in the context of early oceanic abundance before complex life.

Answer:

C. dissolved methane