The correct answer is C. Stratum granulosum.

Note the scaly plaques with some lichenification in the antecubital fossa as most consistent with atopic dermatitis. Atopic dermatitis is often due to a mutation in filaggrin, a histidine-rich protein that is mostly located in the granular layer (i.e., stratum granulosum) and degraded in the corneal layer.

Filaggrin is not most likely to be location in the stratum basale, stratum corneum, stratum lucidum, or stratum spinosum in highest abundance.

References: Hoober JK, Eggink LL. The Discovery and Function of Filaggrin. Int J Mol Sci. 2022;23(3):1455. Published 2022 Jan 27.