The correct answer is A. Neurofibromin.

Neurofibromatosis I occur due to a microdeletion at 17q11.2 involving the NF1 gene, which encodes for neurofibromin. It is an autosomal dominant disorder characterized by numerous benign tumors (neurofibromas) of the peripheral nervous system, cafe au lait macules, freckling in the area of the armpit (Crow’s sign), two or more growths on the iris of the eye (known as Lisch nodules or iris hamartomas), tumor on the optic nerve (optic glioma), abnormal development of the spine (scoliosis), the temple (sphenoid) bone of the skull, or the tibia (one of the long bones of the shin) and a first degree relative (parent, sibling, or child) with NF1.

The other proteins in the list are associated with other syndromes: In neurofibromatosis type 2, a NF2 gene mutation has been identified which encodes for a protein called Merlin, in tuberous sclerosis two genetic mutations have been identified on two separate chromosomes namely tuberin and hamartin, and a Folliculin mutation is seen in Birt Hogg Dube syndrome.