Ans. (a) Thumb sign.Epiglottitis is an infection of the epiglottis which can lead to upper airway obstruction. It is most commonly seen in ages 3 to 6 years, and is most commonly caused by Haemophilus influenza B (HIB). The incidence has decreased 90% since the introduction of the HIB vaccine. Children present with fever, sore throat, and severe odynophagia. They appear sitting up and leaning forward, drooling. They may have biphasic stridor, especially when presenting later. Epiglottitis can be detected radiographically with a lateral cervical plain film, which shows the characteristic "thumbprint sign.' This sign is caused by the thickened epiglottis.Image source- style="font-family: Times New Roman, Times, serif">