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).
The building blocks of proteins are known as amino acids. These acids are not only the building blocks of proteins--they are also important in many other chemical and biological processes.
A scientific law would be your answer.
There are many laws that are defined using formulas.
I hope this helps!
~cupcake
