49; Number of Electrons = Number of Protons = Atomic Number
Hey!
Hope this helps...
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A user mentioned in the comments of one of the answers deleted: "its B" < The user (<span>lolbae0806) had mentioned this...</span>
So I believe the correct answer is:
B.) More oxygen gas became present in the atmosphere.
Answer:
They make proteins, They can float free or be connected to endoplasmic reticulum