Question

multiple choice question
according to our current understanding, how did cellular respiration evolve?
the different steps in cellular respiration evolved over time.
cellular respiration appeared when two organisms merged, combining their metabolic activities.
cellular respiration first appeared as a very long process, and has since been simplified down to the few steps that extract energy most efficiently.
all of the steps in cellular respiration appeared simultaneously in an ancestral organism.

Explanation:

Cellular respiration is a complex process and its different steps are thought to have evolved over time through natural - selection and evolutionary processes. There is no evidence that all steps appeared simultaneously or that it originated from a merger of organisms in the way described, or that it started as a long process and was simplified.

Answer:

The different steps in cellular respiration evolved over time.