Answer:
A. A change in the gene pool over time
Explanation:
The evolution is the change in the gene pool over time. Therefore, the option (A) is the correct answer.
The Roman aqueducts were an important advance in public: A) hygiene
Answer:
Because it usually takes a long time, and is a very long process.
Explanation:
The first known single-celled organisms appeared on Earth about 3.5 billion years ago, roughly a billion years after Earth formed. More complex forms of life took longer to evolve, with the first multicellular animals not appearing until about 600 million years ago.
