What could the writer add to his argument to make it more convincing? a) several quotations from famous poems that relate to the idea of service b) a few descriptions of some volunteer agencies that are available around town c) encouragement of readers to go vote for the issues that matter most to them. d) examples of service projects that also meet curriculum standards for academic classes

D). Examples of service projects that also meet curriculum standards for academic classes.

Explanation:

The author employs variety of techniques(substantial and factual claims, evidences, quotations, sharing of a personal experience, etc.) to make their argument more effective and persuasive.

As per the question, the writer can add  'examples or illustrations of service projects...classes' as these illustrations would assist in explaining the point more clearly and effectively. The illustrations would not only provide support to the ideas but add value and credibility to the claim that would help in stimulating the audience's interest and convincing them reasonably. Thus, option D is the correct answer.