Pruning is a horticultural and silvicultural practice involving the selective removal of parts of a plant, such as branches, buds, or roots.
Reasons for pruning include:
Health: Removing dead, diseased, or damaged branches to improve plant health and prevent spread of disease.
Shape and Structure: Training young plants to a desired form (e.g., for landscape aesthetics, fruit production, or timber quality). Maintaining the shape of mature plants.
Vigor and Productivity: Encouraging new growth, improving flowering or fruiting (e.g., by removing old wood or thinning out branches to improve light penetration and air circulation).
Safety: Removing hazardous branches that might fall or obstruct views/paths.
Size control: Restricting the size of a plant.
Rejuvenation: Stimulating new growth in old or overgrown plants.
The act of pruning involves selectively cutting branches or other plant parts.
Let's evaluate the options:
(a) A live bud from a desired plant is inserted into a host: This describes budding, a method of grafting (asexual plant propagation).
(b) Loosening the ground to remove weeds: This describes weeding or hoeing, a cultivation practice.
(c) The process when individual branches are cut selectively: This is the definition of pruning.
(d) Adding fertilizers to the top soil: This describes fertilizing, a practice to supply nutrients to plants.
Therefore, pruning is the process when individual branches (or other parts) are cut selectively.
\[ \boxed{\text{The process when individual branches are cut selectively}} \]