The correct answer is A. Walking on the sand.

This photo depicts cutaneous larva migrans, which is characterized by tortuous pruritic tracks moving slowly, 2 mm-2cm/day. It lacks collagenase so it is unable to penetrate the basement membrane. Lesions will usually appear on the buttock or feet where contact is made with infested beach sand. Cutaneous larva migrans is caused by larvae of hookworms from dogs and cats (Ancylostoma braziliense or Bunostomum phlebotomum).

Sitting in a hot tub most commonly causes folliculitis. Wading in freshwater can put you at risk for Schistosomiasis, which spares clothing covered skin. Caterpillars can cause dermatitis; most notably the puss caterpillar causing “Railroad’ track” pattern of hemorrhage.

References:

Kollipara R, Peranteau AJ, Nawas ZY, et al. Emerging infectious diseases with cutaneous manifestations: fungal, helminthic, protozoan and ectoparasitic infections. J Am Acad Dermatol. 2016;75:19-30.