Human Population Growth and Overpopulation Can someone please help me I don't understand what I have to do.

all you're trying to do is create a histogram of what has happened in the past and what could happen in the future.

Explanation:

for example and AD you feel the first little bar because it's not more than a billion and its last therefore it would be the zero billion

and then for 1850 you feel to bars because they had 1 billion people so therefore you feel the 0 billion and the 1 billion part

it has one origin of replication, but it proceeds in two directions - d)