The correct option is C Malvaceae
Gossypium is the cotton genus. It belongs to the tribe Gossypieae, in the mallow family, Malvaceae, native to the tropical and subtropical regions from both the Old and New World.
The genus Gossypium comprises around 50 species, making it the largest in species number in the tribe Gossypioieae. New species continue to be discovered. The name of the genus is derived from the Arabic word goz, which refers to a soft substance.
So, Gossypium belongs to the family Malvaceae and not to Cruciferae, Leguminosae and Euphorbiaceae.
Therefore, the correct answer is option C.