I shall finish . . . . . . . . who are absent.

First, let's define the terms involved. Pronouns are words that replace nouns. In this case, we need a pronoun that refers to people who are absent.

Option A, "him," is a singular pronoun, referring to one male person. This is incorrect because the sentence implies multiple absent people.

Option B, "them," is a plural pronoun, referring to multiple people. While grammatically correct in terms of plurality, it lacks the specific demonstrative quality needed.

Option D, "these," is a plural demonstrative pronoun that refers to things nearby. It's inappropriate here as it doesn't specify a distance or location related to the absent people.

Option C, "those," is the correct choice. "Those" is a plural demonstrative pronoun that refers to people or things that are at a distance (physically or figuratively). Since the absent individuals are not present, "those" accurately indicates them. The sentence is correctly completed as: "I shall finish those who are absent." This clearly identifies the group of people the speaker will finish the task for.