Answer:
b. The brain increased in size which resulted in hominids developing tools.
Explanation:
Hominids refers to Primates. They are of four types which include Human, Australopithecus, Paranthropus, and earlier forms such as Sivapithecus. Examples of Hominids include Humans, Chimpanzees, Gorillas etc. They mostly walk on two legs.
Due to their social interaction and food gathering skills their brain increased in size which led to being able to develop tools for their survival.