Step 1: Understanding delegation of authority. 
  
Delegation of authority means assigning responsibility and granting the right to make decisions. For delegation to be effective, authority must accompany responsibility. This ensures that individuals have the power to carry out tasks and make decisions related to those responsibilities. 
Step 2: Analyzing the options. 
  
(A) Authority: Correct. Effective delegation requires that authority is granted along with responsibility. Without authority, the responsibility becomes ineffective. 
  
(B) Man-power: This is not the correct answer because while manpower is important, it is not directly related to the delegation of authority. 
  
(C) Incentive: Incentives can motivate employees but are not directly related to the effective delegation of authority. 
  
(D) Promotion: This is incorrect as promotion is a form of career advancement, not related to the delegation of authority. 
Step 3: Conclusion. 
  
The correct answer is (A) Authority, as it is essential for effective delegation.