The Present Concern Over the Apparent Increase in the Temperature

The present concern over the apparent increase in the temperature of the biosphere is the "greenhouse effect" caused primarily by the

A) decrease in the human population on earth.
B) increase in carbon dioxide in the atmosphere from the burning of fossil fuels.
C) increased photosynthesis from increased carbon dioxide.
D) conversion of grasslands to farmlands.
E) increases in the tropical forest biome.