Final answer:
In APA style, when citing a text by six or more authors, the correct in-text citation is the surname of the first author followed by 'et al.' and the year of publication (e.g., Smith et al., 2021).
Step-by-step explanation:
The subject of this question is the appropriate formatting for an in-text citation in APA style when citing a text by six or more authors. In such cases, the correct in-text citation should include the surname of the first author followed by 'et al.' and the year of publication. For instance, if the first author's last name is Smith and the work was published in 2021, the in-text citation would appear as (Smith et al., 2021). This format is used both for parenthetical and narrative in-text citations throughout the paper after the initial citation of the source. If a source has six or more authors, the first author's last name followed by 'et al.' is used in all subsequent citations. It is worth noting, however, that in the reference list at the end of your paper, all authors must be listed for sources with up to 20 authors. For sources with more than 20 authors, the first 19 authors are listed, followed by an ellipsis (...), and then the final author's name, without including 'et al.'.