The correct option is B Malvaceae
Fibres are usually obtained from the members of Malvaceae. The Malvaceae or the mallows, are a family of flowering plants estimated to contain 243 genera with 4225+ species. Well-known members of this family include okra, cotton and cacao. Fibers are obtained from cotton plant and cotton is grown commercially in large extent for fiber.
Therefore, the correct answer is option B.