Use the Following Graph and Information to Answer the Question

Multiple Choice

Use the following graph and information to answer the question below.
Flycatcher birds that migrate from Africa to Europe feed their nestlings a diet that is almost exclusively moth caterpillars. The graph shows the mean dates of arrival, bird hatching, and peak caterpillar season for the years 1980 and 2000.
The shift in the peak of caterpillar season is most likely due to ________.

A) pesticide use
B) earlier migration returns of flycatchers
C) an innate change in the biological clock of the caterpillars
D) global warming
E) acid precipitation in Europe