Which of the following is not a medical requirement for a Second-Class Medical Certificate?

The correct reasoning behind the choice provided is that having 20/20 vision is not an absolute requirement for obtaining a Second-Class Medical Certificate. Instead, the FAA requires that vision must be sufficient to perceive colors necessary for the safe performance of airman duties and that applicants must demonstrate 20/40 vision or better in at least one eye, either with or without correction. The requirement focuses on functional vision rather than a specific standard like 20/20.

In contrast, being able to read and speak English is pertinent for communication and safety in aviation, as is the absence of disqualifying medical conditions that could impair a pilot's ability to operate an aircraft safely. A history of substance abuse is also significant, as it raises concerns about a pilot's fitness to fly and may lead to a denial of the medical certificate if it poses a risk to safety.