As shown in the figure, it is a schematic diagram of the process of vegetative propagation of plants. The specific vegetative propagation mode shown in the figure and the names represented by parts A and B are () respectively. Grafting refers to grafting the bud or branch of one plant to another plant, so that the two parts can grow together into a complete plant.

Grafting is divided into branch grafting and bud grafting. Bud grafting is called bud grafting, and branch grafting is called branch grafting. It can be judged from the picture that the grafting of B bud (scion) onto A rootstock is bud grafting.

So choose: B.