Question

why do we think that dna and the metabolic pathways used by living things developed early in the history of life on earth?
they are complicated
they are common to most life forms
they do aerobic respiration

Explanation:

DNA and metabolic pathways are fundamental and shared by most life - forms. This suggests they evolved early and were conserved over time. Complicated nature doesn't imply early development, and not all life with early - developed DNA and metabolic pathways do aerobic respiration.

Answer:

They are common to most life forms