Final answer:
Option (4), In Chicago style citation, for a work with four or more authors, use 'et al.' after the first author. For works with three or fewer authors, list all names. With exactly four authors, list all four in the citation.
Step-by-step explanation:
In Chicago style citation for works with multiple authors, the formatting will change depending on the number of authors. If a work has four or more authors, you should list the name of the first author followed by "et al." which stands for "and others." This abbreviation is used to indicate that additional authors contributed to the work. An example of this format would look like: "Barlow, David H., et al. Abnormal Psychology: An Integrative Approach. 8th ed., Cengage Learning, 2017."
However, when there are three or fewer authors, you should list all their names in the reference. For two or three authors, the format looks like this: "Author1, Author2, and Author3." When there are exactly four authors, you should list all four, such as "Author1, Author2, Author3, and Author4." Therefore, the correct answer to your question would be option 4) Author1, Author2, Author3, and Author4.