Final answer:
None of the traits listed — power grip, precision grip, and opposable thumb — are unique to hominins because other primates also have these adaptations for climbing trees, which include the opposable thumb and the ability to grip.
Step-by-step explanation:
Among the options given — power grip, precision grip, and opposable thumb — which are unique to hominins, the correct answer is none of these are correct. All of these traits are found in primates in general. Hominins, which include Homo sapiens and our closest extinct relatives, do possess these traits, but they are not unique to hominins as other primates also have these adaptations for climbing trees, such as opposable thumbs and the ability to grip.
Both hominins and primates have the capability for a power grip and a precision grip. These features facilitate interactions with the environment, which have been important for the survival and evolution of these groups. The development of a precision grip, in particular, has allowed for the use of tools, an important aspect of hominin evolution. However, the question was specifically about which trait is unique to hominins, and since other primates also have opposable thumbs and similar gripping abilities, none of the choices listed are exclusive to hominin species.