4. The author mentions the best-seller lists and the Book-of-the-Month Club primarily to emphasize Raintree County's:

Answer: C

Explanation:

Raintree County achieved significant commercial success.

The author highlights the best-seller lists and the Book-of-the-Month Club selection to underscore the commercial success of Raintree County, indicating its popularity and wide readership at the time of its publication.

A) limited readership

This option is incorrect because the mention of best-seller lists and the Book-of-the-Month Club selection suggests that Raintree County had a large readership, contrary to the idea of being limited in audience.

B) enduring appeal

While Raintree County may have had some lasting significance, the emphasis in the extract is on its initial success and popularity rather than its long-term appeal, making this option not the primary focus of the author's mention.

C) commercial success

This option is correct as the author refers to the best-seller lists and the Book-of-the-Month Club to illustrate Raintree County's commercial success, highlighting its achievement in the literary market at the time.

D) artistic aspirations

Although the novel aspired to be The Great American Novel, the context of the extract focuses more on its commercial success rather than its artistic ambitions, thus rendering this option less relevant to the primary emphasis.

Conclusion

The mention of best-seller lists and the Book-of-the-Month Club clearly indicates that Raintree County experienced substantial commercial success, which is the main point the author wishes to convey. Other options fail to capture this focus, emphasizing the popularity and market performance of the novel rather than its readership limitations, enduring appeal, or artistic aspirations.