Rash appears in children & young adults, etiology unknown, no epidemics, not contagious, evolves over weeks. Starts with a single salmon-colored lesion with a raised border on the trunk, 1-5 cm & then over 1-2 weeks spreads following the ribs. What is this rash?

a) Psoriasis
b) Pityriasis rosea
c) Eczema
d) Lyme disease