Correct answer: "both a and b" - chimpanzees and gorillas
There are studies that date from around the 1970's where chimpanzees and gorillas were taught American Sign Language. They were able to learn several hand signs and, in one of the cases, even teach some to an adopted son. Some of these famous chimpanzees and gorillas are Washoe and her adopted son, Loulis, Nim Chimpsky, and Koko, the gorilla.
