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the graph shows data from a decades-long study of cliff swallows, which nest along highway overpasses. the solid line represents the population of living cliff swallows; the dotted line represents that of cliff swallows found as roadkill.

which conclusion is best supported by the data shown?
a) differences in wing length are leading to speciation within the population.
b) individuals with longer wings are out-competing individuals with shorter wings.
c) alleles for shorter wings increase fitness, causing a change in the population’s gene pool.
d) deaths due to vehicular traffic are increasing, causing the cliff swallow population to decline.