The final product C, obtained in this reaction would be

 To get a mono bromo compound, before bromination the amino group is acetylated. After bromination, bromoacetanilide is acid hydrolyzed to form the desired halogenated amine. Ethane is an alkane and forms monobromo derivatives. Methane is an alkane with one carbon atom and forms a monobromo derivative.

Therefore, option D is correct.