A 13-year-old boy developed malaise, anorexia, fevers, tender submandibular lymphadenopathy, localized pain, burning around his mouth, then painful grouped vesicles appeared on erythematous base. These vesicles then progressed to pustules, erosions, and ulcerations. What is the most likely diagnosis?
a) Stevens-Johnson syndrome
b) Herpangina
c) Erythema multiforme (EM) major
d) Aphthous stomatitis
e) Herpes simplex virus infection