How should online sources without a publication date be cited in APA format?

In APA format, when citing online sources without a publication date, the correct approach is to use "n.d." which stands for "no date." This designation clearly indicates to the reader that no specific publication date is available for the source, maintaining clarity and transparency in citation practices.

Using "n.d." is consistent with APA guidelines, which aim to provide concise and standardized citations. This helps ensure that readers can easily understand the nature of the source, especially in academic and professional contexts where the timeliness of information may affect its credibility.

The other choices do not align with the established APA format. For instance, "unknown date" and "no date available" are not standardized terms in APA, and using "n.a." does not convey the intended meaning regarding the absence of a publication date in the same accepted way as "n.d." does. Therefore, using "n.d." is the most appropriate and correct option for citing sources lacking a publication date in APA format.