is a philosophy that implies selective dispersal of authority because it propagates the belief that people are competent, capable and resourceful.

The correct option is Decentralisation.

Explanation:

Decentralisation refers to the systematic and selective dispersal of decision-making authority to the lower levels of management in an organization.
It is based on the philosophy that employees at all levels are competent, capable, and resourceful, and therefore can make decisions regarding their own work domains without constant supervision or top-down control.

Let's look at why other options are incorrect:
1. Span of management refers to the number of subordinates that a manager can effectively supervise, which is a structural metric rather than a philosophy of authority dispersal.
2. Centralisation is the concentration of decision-making authority at the top levels of management, which is the opposite of dispersal.
3. Democratic leadership style is a style of leadership where subordinates are involved in decision-making, but it does not represent the structural dispersal of authority throughout the entire organization.