Obscure :

Answer: Option C

Implicit : inherent, latent, ingrained, inherent, vested, latent, tacit.
Obnoxious : extremely unpleasant.
Pedantic : excessively concerned with minor details or rules, over scrupulous.

Explicit : stated clearly and in detail, leaving no room for confusion or doubt.
Obscure : not discovered or known about, uncertain

Antonym of Obscure is Explicit.