How does pruning help in making the hedge dense?
(a) The apical shoot grows faster after pruning
(b) It releases wound hormones
(c) It induces the differentiation of new shoots from the rootstock
(d) It frees axillary buds from apical dominance

Hint: This is thought to be due to the production of auxins in the stem tips, the growing apical bud inhibits the growth of the lateral axillary buds. Parts of the plant which do not play an important role are removed by the pruning technique.

Complete answer:
Pruning is the removal of unwanted parts of a plant that are not requisite to growth or production. It is a horticulture technique that is mainly used in orchard and vineyard management for improving flowering and fruiting. In some plants, it is also done to enhance plant shape and growth.
Hedges usually require formative pruning in winter and early spring. This way the hedges can be safeguarded from damage and pests. Any healthy shrub has two hormones that regulate growth. Auxin is one of them which is produced by leaves and buds while cytokinins is another important growth-regulating hormone that is produced by roots. Due to strong upward growth in shoots, the growth of lateral buds can be suppressed. But when the hedge is pruned the repressive auxin signal and the buds will break. So if a hedge is pruned regularly it will respond by becoming more denser and the regrowth will be a bunch of small shoots until one of the shoots grows and dominates and suppresses the growth. This is also known as apical dominance.

Additional information:
There are several types of pruning. Some of them are listed below:
-Thinning: This procedure includes the removal of branches at the base of a plant.
-Topping: In this, the branches which are down to the trunk are removed to help them grow in a specific way.
-Raising: This process includes trimming of low hanging branches.
-Reduction: It includes trimming the volume of the tree for safety purposes.

So, the correct answer is ‘It frees axillary buds from apical dominance’.

Note:
Pruning promotes the healthy growth of the plant as it removes dead branches and leads to higher production. Strong apical dominance is beneficial, as in the "Ballerina" apple trees. These trees are considered to be grown in small gardens, and their strong apical dominance merge with a dwarfing rootstock produce a dense narrow tree with very small fruiting side branches.