The word that best completes this sentence is b. inherent: Oliver had an inherent ability as a wide receiver, naturally dodging tackles and making his way down the football field.
"Inherent" is the word that best completes the sentence because it is an adjective that makes reference to a permanent attribute. Moreover, it is used to refer to something that someone is born with. In the case of this sentence, the writer wants to indicate that the ability that Oliver has is a natural part of him ("naturally dodging tackles") and that is why the word that best fills in the blank is "inherent".