Solution

Brassica nigra (black mustard) is an annual weedy plant cultivated for its seeds, which are commonly used as a spice. The spice is generally made from ground seeds of the plant, with the seed coats removed. The small seeds are hard and vary in color from dark brown to black. Brassica juncea (leaf mustard), Brassica napus (rape seed) and Brassica campastris (field mushroom) are not the botanical names of black mustard.
Therefore, the correct answer is option A.