Which of the following statements about chimpanzees is true?
A. Chimpanzees are able to produce spoken language but not signed language.
B. Under the right conditions, chimpanzees can learn to use human language at the same level of proficiency as two-year-old human children.
C. Chimpanzees are incapable of using any form of human language.
D. It is easier to teach a fully grown chimpanzee human language than it is to teach an infant or adolescent chimpanzee human language