Posner and His Colleagues Had Participants View Two Letters and Respond

Posner and his colleagues had participants view two letters and respond according to whether these letters were both vowels, both consonants, or one of each. Participants were fastest when viewing two physically identical letters, somewhat slower when viewing the same letter in two different fonts, and slowest in the case where two different consonants were presented. This finding shows that

A) we form multiple representations of stimuli.
B) we form representations of stimuli based only on their physical attributes.
C) we form representations of stimuli based only on their abstract category membership.
D) more complex mental representations produce faster reaction times.