The correct answer is A. Lichen planus.
Lichen planus thins the nail plate, which may become grooved and ridged. The nail may darken, thicken, or lift off the nail bed (onycholysis). Sometimes the cuticle is destroyed and forms a scar (pterygium). The nails may shed or stop growing altogether, and they may rarely, completely disappear (anonychia).
Although most frequently associated with lichen planus, dorsal pterygium may also occur in Stevens-Johnson syndrome and after trauma albeit less frequently.
Alopecia areata is associated with nail findings such as pitting, ridging, and trachyonychia.
Half-and-half nails occur in renal failure.
1. Le Cleach L, Chosidow O. Clinical practice. Lichen planus. N Engl J Med. 2012 Feb 23;366(8):723-32. doi: 10.1056/NEJMcp1103641. PMID: 22356325.