The correct option is
A Shoot system.
Grafting is a horticulture technique where the living detached portion of the plant is used to regenerate the growth. One plant is selected for its roots and this is called the stock or rootstock. Scion is the detached living part of the plant which is selected for its stems, leaves, flowers, or fruits and generates the shoot system. The joining of scion and stalk is known as inosculation. The techniques is mostly used in asexual mode of reproduction.
So, the correct answer is option A.