Sexual reproduction refers to the process that the sperm of bisexual germ cells combine with egg cells to form fertilized eggs, and the fertilized eggs develop into new individuals. Asexual reproduction refers to the process that a new individual is directly produced by the mother without the combination of hermaphroditic germ cells. The way in which plants propagate with vegetative organs such as roots, stems and leaves is called vegetative propagation. Artificial asexual propagation methods include grafting, cutting and layering. The embryo of the seed is developed from the fertilized egg and has been combined with the hermaphroditic germ cells. Therefore, in Option A and Option B, sweet potatoes are propagated by roots and potatoes by stems, all of which are propagated by vegetative organs and asexually.

So choose: B.