Observations Collected by Agencies Such as the National Aeronautics and Space

Observations collected by agencies such as the National Aeronautics and Space Administration (NASA) suggest that during the last half century,average global temperatures: 

A) did not greatly vary. 
B) increased by about 0.74 degrees Celsius. 
C) decreased significantly, by about 3.4 degrees Celsius. 
D) increased by about 1.2 degrees Celsius. 
E) decreased by about 0.03 degrees Celsius.