How did Saporito and colleagues (2007) conclude that the bright coloration of O. pumilio frogs functions as an aposematic signal?

A) Colorful models were attacked less often than cryptic models.
B) Models on a white background were attacked most often.
C) Cryptic models were never attacked.
D) Birds attacked colorful models before attacking cryptic models.
E) Birds became sick after attacking colorful models.