The correct option is A Grafting
Grafting is the technique whereby tissues from one plant are inserted into those of another so that the two sets of vascular tissues may join together.
Layering is a means of plant propagation in which a portion of an aerial stem grows roots while still attached to the parent plant and then detaches as an independent plant.
Twin scaling is a method of propagating plant bulbs. Twin-scaling is practiced by professional growers and skilled amateurs to increase bulbs that would naturally propagate very slowly.
Plant cutting, also known as striking or cloning, is a technique for vegetatively (asexually) propagating plants in which a piece of the stem or root of the source plant is placed in a suitable medium such as moist soil, potting mix, coir or rockwool. The cutting produces new roots, stems or both, and thus becomes a new plant independent of the parent.
Thus, the correct answer is option (A), 'Grafting'.