The increase in the concentration of CO2 in our environment in last fifty years; since 1960 is about _________

The increase in the concentration of CO2 in our environment in last f

1.	The increase in the concentration of CO2 in our environment in last fifty years; since 1960 is about _________
A.	20%
B.	10%
C.	14%
D.	6%
Answer» D. 6%