The correct answer is E. Cytarabine.

This patient developed neutrophilic eccrine hidradenitis, a toxic disorder of the sweat glands commonly associated with chemotherapeutic agents. The eruption is thought to result from the direct cytotoxic effects of chemotherapy of eccrine glands. Commonly implicated drugs include cytarabine, danorubicin, bleomycin, and cyclophosphamide.

Sorafenib is a tyrosine kinase inhibitor associated with hand, foot, and mouth skin reactions. Acyclovir, valacyclovir, and etoposide are not associated with a similar response.

References:

Bolognia, J., In Schaffer, J. V., & In Cerroni, L. Elsevier, 2018. Dermatology. (Ch.39)