The sound explanation is that the Sea organisms released oxygen into the ocean until the ocean couldn't absorb anymore, then, it was then released into the atmosphere from the ocean
Fossils gives geologist some information about the organism that lived in the past because when those organism dies, they decay and goes deep into the lithosphere.
Basically, the plant life in the ocean does produce oxygen for the animal in the ocean because its produce oxygen and other produce carbon(ix)oxide.
Hence, the sound explanation is that the Sea organisms released oxygen into the ocean until the ocean couldn't absorb anymore, then, it was then released into the atmosphere from the ocean
Therefore, the Option A is correct.
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