Bonobo Kanzi's (Pan Paniscus) Use of Language (Savage-Rumbaugh Et Al

Bonobo Kanzi's (Pan paniscus) use of language (Savage-Rumbaugh et al. 2001) is unique in that he

A) has demonstrated an understanding of spoken English by correctly carrying out requests, even if they are rather bizarre.
B) spontaneously produces vocalizations many times a day that differ in content and are associated with items or actions in his environment.
C) was never explicitly trained to use lexigrams. He simply acquired the skill by observing his mother's training sessions.
D) all of the above.