The Main Cause of the Increase in the Amount of CO₂

Multiple Choice

The main cause of the increase in the amount of CO₂ in Earth's atmosphere over the past 150 years is

A) increased worldwide primary production.
B) increased worldwide standing crop.
C) an increase in the amount of infrared radiation absorbed by the atmosphere.
D) the burning of larger amounts of wood and fossil fuels.
E) additional respiration by the rapidly growing human population.