Observations collected by agencies such as the National Aeronautics and Space Administration suggest that during the last half century, average global temperatures:
A) did not greatly vary.
B) increased by about 0.74 degree Celsius.
C) decreased significantly by about 3.4 degree Celsius.
D) increased by about 1.2 degree Celsius.
E) decreased by about 0.03 degree Celsius.
Question 2
Most climatologists believe that the recent climate change is the result of human activities, especially the release of:
A) noble gases.
B) inert gases.
C) greenhouse gases.
D) dielectric gases.
E) insulating gases.
