Step 1: Understanding Staffing. 
  
Staffing is a critical function in both personnel management and overall management. It involves acquiring, deploying, and retaining a workforce for an organization. Staffing is part of organizational functions and plays a role in personnel management as well as management itself. 
Step 2: Analyzing the options. 
  
(A) Part of organisation: Correct. Staffing is indeed a part of the organizational process, ensuring that the right people are placed in the right positions. 
  
(B) Function of personnel management: Correct. Staffing is directly related to personnel management as it involves hiring, training, and retaining employees. 
  
(C) Function of management: Correct. Staffing is a core function of management, as it ensures the organization has the necessary human resources. 
  
(D) All of these: Correct. Staffing is an integral part of both organizational processes and management functions. 
Step 3: Conclusion. 
  
The correct answer is (D) All of these, as staffing is crucial for both the personnel management function and the broader management function within an organization.