What format is used to display the date in the report header?

The correct answer is the choice that uses the format "31-May-19" because it presents the date in a clear and comprehensive manner that is often used in formal reports. This format includes the day, the full name of the month, and the last two digits of the year. This style enhances readability by avoiding numeric ambiguity, as different regions might interpret numeric date formats differently. For instance, "31-05-19" could be interpreted as either May 31 or the 31st day of May, depending on the local customs.

This date format is particularly prevalent in professional settings where clarity is paramount, as it leaves no room for misunderstanding about what month is being referenced. Furthermore, it aligns with the convention used in business and academic contexts, making it beneficial for reports that aim to communicate information clearly and effectively.