Which of the following best describes the author's attitude toward the increasing amount of carbon dioxide in the atmosphere and its consequences

A．discuss the significance of increasing the amount of carbon dioxide in the atmosphere
B．warn of the dangers of continued burning of fossil fuels
C．explain how a constant temperature is maintained in the Earth's surface
D．demonstrate the usefulness of mathematical models in predicting long-range climatic change

A．Fossil fuels were burned for the first time.
B．The average temperature at the Earth's surface has become 2℃ cooler.
C．The amount of carbon dioxide in the atmosphere has increased measurably.
D．The amount of farmland worldwide has double