The correct option would be b.
Vesicles. Vesicles are small, fluid-filled lesions on the skin that are common in cases of urticaria. The presence of vesicular lesions on WP's trunk and arms would confirm the suspected diagnosis. It should be noted that erythematous papules, wheals, and pustules are also common in cases of urticaria. Erythema means redness, while papules are small flat lesions, wheals are raised lesion with a pale center, and pustules are pus-filled lesions.