Concept:Grafting is a vegetative propagation method in which two parts of plants are joined so they grow as a single plant.
Explanation:In grafting, a shoot piece called the scion is cut from one crop plant.
The scion is joined firmly to the lower rooted part, called the rootstock, of another plant.
The two parts must belong to closely related crops so their tissues can unite and heal correctly.
After joining, they continue to grow as one plant, combining the root system of the rootstock with the shoot system of the scion.
Option A is wrong because grafting does not involve fusion of gametes; that describes sexual reproduction.
Option C is wrong because the transfer of only a bud is a separate technique called budding.
Thus, grafting is the joining of two parts from related crops.
Answer:D. the joining of two parts from related crops