Staffing is a crucial function in organizations today due to various factors, such as the advancement of technology, the increasing size of organizations, and the complicated behavior of human beings. Each of these factors contributes to the importance of staffing in different ways.

Advancement of Technology:
- Technological advancements have transformed the way organizations operate and have introduced new complexities in managing human resources.
- With the advent of automation and artificial intelligence, organizations need to ensure they have the right skill sets in their workforce to leverage these technologies effectively.
- Staffing becomes essential in identifying and hiring individuals with the required technical expertise and adaptability to work in a technologically advanced environment.
- Additionally, as technology evolves rapidly, organizations need to continuously update and train their existing workforce to keep up with the changes.

Increasing Size of Organizations:
- As organizations grow in size, the complexity of managing human resources also increases.
- Larger organizations require a larger workforce to handle various tasks and functions, making staffing a critical process.
- Staffing helps in identifying the right number of employees needed and recruiting individuals with the necessary qualifications and experience to fill the positions.
- Moreover, as organizations expand, they may also need to establish new departments or divisions, requiring recruitment and staffing efforts to ensure these new units are properly staffed.

Complicated Behavior of Human Beings:
- Human behavior can be complex and unpredictable, making it challenging for organizations to manage their workforce effectively.
- Staffing plays a vital role in understanding the behavioral aspects of employees and aligning their skills, personalities, and motivations with job requirements.
- Through careful selection and placement, organizations can ensure a better fit between employees and their roles, resulting in increased job satisfaction, productivity, and retention.
- Additionally, staffing also involves managing conflicts, promoting teamwork, and fostering a positive work environment, all of which contribute to managing the complicated behavior of human beings.

In conclusion, the correct answer is option 'D' - all of these factors contribute to the importance of staffing in organizations. The advancement of technology, increasing size of organizations, and complicated behavior of human beings necessitate effective staffing practices to ensure a capable and productive workforce.