Which of the following is a characteristic of Koplik spots in children with measles?

A. They appear as small, red spots with white centers on the buccal mucosa. Koplik spots are a pathognomonic sign of the prodromal phase of rubeola. These lesions are typically located opposite the molar teeth and resemble grains of salt on a red background. Identification allows for early diagnosis before the characteristic maculopapular rash appears. B. They are enlarged parotid glands. Swelling of the parotid glands is the clinical hallmark of mumps, not measles. Parotitis involves inflammation of the salivary glands leading to visible jaw swelling and discomfort. Measles involves respiratory and systemic symptoms rather than localized glandular hypertrophy in the jaw. C. They present as fluid-filled vesicles on the child's chest. Fluid-filled vesicles are characteristic of varicella or herpes zoster infections. Measles presents with a flat, red, confluent rash that begins on the face and spreads downward. Vesicular lesions indicate a different viral etiology or a secondary integumentary complication. D. They are a gray pseudomembrane covering the pharynx. A thick, gray, adherent pseudomembrane is the classic diagnostic finding for diphtheria. This membrane can cause significant airway obstruction and is composed of dead tissue and fibrin. Measles causes mucosal inflammation but does not produce this specific obstructive fibrinous coating.