Which of the following is a disqualifying condition related to respiratory safety?

Hypoxemia at rest is a disqualifying condition related to respiratory safety because it indicates that an individual has insufficient oxygen levels in their blood while at rest. This condition suggests the presence of underlying respiratory issues that can significantly impair a person's ability to perform tasks that require physical exertion or concentration, such as driving or operating heavy machinery. When someone experiences hypoxemia, their body's ability to function effectively is compromised, which poses a safety risk not only to the individual but also to others.

In contrast, the other options may represent conditions that can often be managed or are not necessarily disqualifying on their own. Stable exercise-induced asthma, for example, can typically be managed with medication and does not necessarily result in ongoing impairment. A well-managed chronic cough may not impact one's overall respiratory function significantly enough to be disqualifying, and shortness of breath during exercise may not be a concern if it does not occur at rest and is not indicative of more severe lung dysfunction. Therefore, hypoxemia at rest stands out as a critical concern that directly affects respiratory capacity and the ability to ensure safety in various activities.