Homeotic genes
a. encode transcription factors that control the expression of genes responsible for specific anatomical structures.
b. are found only in drosophila and other arthropods.
c. are the only genes that contain the homeobox domain.
d. encode proteins that form anatomical structures in the fly.

a. encode transcription factors that control the expression of genes

Explanation:

Homeotic Genes - They encode transcription factors that determine the location at which specific structures develop. They give organs identity. Homeotic genes act as regulators of development and some mutations found in flies were instrumental in unraveling the macroevolution related mysteries.

Mutations in homeotic genes are often fatal in the early stages of development, however viable mutant flies with strange aberrations have been found, such as the discovery of Antennapedia mutants, in which paws are formed in place of antennae. Homeotic genes regulate the development of specific embryonic segments and are fundamental, among other functions, in determining the anteroposterior axis of metazoans. When we compare flies and humans, homeotic genes resemble both their nucleotide sequence and their relative position on chromosomes.

c is the correct answer!