In which of the following patients can nasopharyngeal airways be used?

Nasopharyngeal airways are designed to help maintain airway patency in patients who may not be able to maintain it themselves due to altered levels of consciousness. They are particularly useful in patients who are semiconscious or unconscious, as they allow for ventilation without relying on spontaneous breathing efforts. The nasopharyngeal airway's structure facilitates insertion through the nasal passage and helps bypass any obstructions in the oral cavity or pharynx.

The use of this type of airway in semiconscious or unconscious patients is crucial because these individuals may have an impaired gag reflex or altered muscle tone, making it difficult for them to maintain an open airway. In contrast, using a nasopharyngeal airway in fully conscious patients can trigger discomfort or the gag reflex, which may lead to complications.

Therefore, the correct answer emphasizes its applicability to patients who are semiconscious or unconscious, making it a vital tool in the management of airway obstruction in those with compromised levels of consciousness.