Answer:
C geosphere
Explanation:
Hydrosphere is realted to water, biosphere is related to living organisms, & atmosphere realtes to air that surrounds us.
"Geo-" relates to the earth.
Well we know that it is not A or C, Reason: Some states have up to 5m people in it. (For example about 8 live in just new York alone.)
And we also know its not 10 billion. Reason for this: Scientist have proven that there is no more then 8 billion people today.
And so now we got 6.5 billion is the closest, the real number is about 7.5 billion.
<span />
Because the men who were at the front came back to their home and made love to their wife. There was also a great feeling of prosperity in the victorious countries.