D

Explanation:
Effective communication facilitates decentralisation by enabling better coordination and information flow across different levels and units of an organisation. It supports decision-making at lower levels without requiring constant oversight from central management. Option A, an authoritarian management style, typically promotes centralisation by concentrating decision-making power. Option B, a larger organisation size, does not inherently increase decentralisation, as it may lead to complexity that could require either centralised or decentralised approaches depending on other factors. Option C, slow technological change, is less relevant, as rapid technological advancements are more likely to necessitate decentralised decision-making to adapt quickly. The answer is supported by the provided document, which states that effective communication can achieve more decentralisation.