The correct option is B Testa/seed coat
The seed usually has two coverings, testa and tegmen. Tegmen is the inner layer whereas testa is the outer layer. The brownish/blackish part seen on the outer side of coconut is testa. The endocarp in coconut is the hard and woody layer just outside the seed. The endosperm is the water filled inside the green coconuts. So, the correct answer is 'Testa/seed coat'.