Step 1: Understand coordination.
Coordination is a necessary management function to ensure that various parts of an organization are working towards common objectives.
Step 2: Evaluate the options.
- Coordination is essential for effective communication and efficient operations.
- It is not voluntary, unnecessary, or a waste of time, as these would hinder organizational effectiveness.
Step 3: Conclude.
Coordination is a necessary function for ensuring that resources are utilized effectively and goals are met.
Final Answer:
\[
\boxed{\text{Necessary}}
\]