The correct answer is d. 3.5 billion years.
Prokaryotes were the first forms of life on Earth long before simple multicellular life appeared because of their ability to withstand extreme conditions. It is believed that the first living forms were bacteria combined with archaea in the microbial mat (multi-layered sheet).
<h2>As carbon dioxide in the process of photosynthesis</h2>
Migration i think is the answer
The horsehoe crab because it was one of the first animals to ever live on earth