The correct answer is B. Erythema dyschromicum perstans.
The photo and histology are diagnostic of EDP (aka Ashy Dermatosis), a benign condition characterized by sudden onset of symmetric, blue-brown, asymptomatic macules. Onset is typically before 40 y/o and occurs in skin types III and IV. Histology shows sparse perivascular infiltrate with melanophages and pigmentary incontinence.
Pityriasis rosea typically occurs between 10-35 years of age and is caused by HHV7>HHV6. It typically occurs with salmon colored macules and papules with collarettes of scale. On pathology, mounds of parakeratosis over slight acanthosis and spongiosis are seen. There is a superficial lymphocytic perivascular infiltrate and extravasated RBCs in the papillary dermis.
Café-au-lait macules are typically present in 10% of the Caucasian population. It typically looks normal at low power.