Another name for the Paleolithic era is is the Stone Age, so it is the second choice.
Answer:
Methane is found deep in the Earth's crust, which makes it difficult to harvest
Explanation:
According to the Scientific American: <em>"With drillers tapping into massive stores of natural gas across the United States, scientists are researching ways to capture it more effectively"</em>. On the same article, you can find that: <em>"Energy companies are looking for a cheap way to separate these gases to yield a pure methane stream"</em>. So it is hard and expensive to harvest methane, even though drillers keep finding it.
I believe the answer is: <span>. Institutional Review Board (IRB)
</span><span>. Institutional Review Board (IRB) was initially created in order to prevent the abuse that happened in many method of research in 20th century..
</span>Because of this institution, researchers nowadays have to follow very strict standards that would limit what they can and couldn't do in their research.
Answer:
The constitution, the Supreme court, the judiciary
Answer: they conquered the independent city states and united them.