The correct answer is D. Halobetasol 0.05% ointment twice daily to affected areas.

The patient has psoriasis with 8% body surface area with no treatment trial previously. The most reasonable next step is to begin a potent topical steroid on the areas with psoriasis on the legs twice daily. Occlusion of the steroid at night can be considered if the patient is not responsive to topical steroids or if the steroid tends to rub off at night onto the bed.

The patient does not have a body surface area greater than 10%, and thus choices such as infliximab or guselkumab is not an appropriate initial treatment. If the patient has psoriatic arthritis, then biologics may be considered. Narrowband UVB to the body 3 times weekly might be too extensive for someone with limited skin disease. However, excimer laser could be considered. Apremilast may also be considered, but this is not the best first treatment for this patient.

References:

Rivera AM1, Hsu S. Topical halobetasol propionate in the treatment of plaque psoriasis: a review. Am J Clin Dermatol. 2005;6(5):311-6.