What was the approximate size of the human population in the 1960's and in 2011?
A - 3 billion in the 1960's and 9 billion in 2011
B - 6 billion in the 1960's and 9 billion in 2011
C - 3 billion in the 1960's and 7 billion in 2011
D - 3 billion in the 1960's and 6 billion in 2011
Answer: C - 3 billion in the 1960's and 7 billion in 2011