Which one A? B? C? D?

A person standing in the penumbra would see a partial eclipse.

Therefore, D.

euniquereni is right, D

there are no options provided but you can choose among the following gender-neutral pronouns: zir, hir, eir, vis, tem, eir.

in the normal course of maintaining a pronoun-antecedent agreement, we could have used the words his or her but since we are also required to use gender-neutral language, we need to replace it with its equivalent gender-neutral pronoun.