Habitability generally refers to an environment capable of sustaining
A) human life
B) plant life
C) microbial life only
D) any kind of life
Question 2
Evidence that the recent rise in carbon dioxide concentration is due to human activity and not natural factors comes from
A) the amount of the rise in the atmospheric concentration tracks almost perfectly with the amount of carbon dioxide being released by industry
B) estimates of changes in the amount of carbon dioxide from natural sources such as volcanoes and the oceans can account for no more than about 1 of the rise in the atmospheric concentration
C) the ratio of carbon isotopes is consistent with the increase in carbon dioxide levels coming primarily from the burning of fossil fuels
D) all of these constitute evidence