Oxygen first began to accumulate in Earth's atmosphere as a result of .
A) biosynthesis
B) cellular respiration
C) methane synthesis
D) photosynthesis

Name: Oxygen first began to accumulate in Earth's atmosphere as a result of . A) biosynthesis B) cellular respiration C) methane synthesis D) photosynthesis
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Oxygen began to accumulate in Earth's atmosphere primarily due to photosynthesis carried out by cyanobacteria, which released oxygen as a byproduct.

Oxygen First Began to Accumulate in Earth's Atmosphere as a Result