Final answer:
The correct answer is option b, as hominins are defined by bipedal locomotion and a nonhoning chewing complex, and are distinct from hominids which include all great apes.
Step-by-step explanation:
A hominin is traditionally defined by two obligate behaviors: bipedal locomotion and a nonhoning chewing complex. The correct answer to the student question is option b - bipedal locomotion and nonhoning chewing complex. Hominins include species in direct lineage to humans, such as the genera Homo, Australopithecus, Paranthropus, and Ardipithecus. They are distinguished from hominids, which encompass all modern and extinct great apes, including humans. The evolution of bipedalism in hominins was a significant adaptation that provided various advantages, such as energy efficiency and the ability to use hands for other purposes like carrying tools and food.