Researchers Who Are Convinced That Animals Can Think Point to Evidence

Researchers who are convinced that animals can think point to evidence that

A) chimpanzees demonstrate the ability to "count" by learning to touch pictures of objects in ascending numerical order.
B) chimpanzees regularly use sticks as tools in their natural habitats.
C) chimps invent grooming and courtship customs and pass them on to their peers.
D) they exhibit all of these skills.