The correct answer is C. system approach.

Operation research, facility layout, and MIS are all examples of systems thinking. Systems thinking is a holistic approach to problem solving that considers the interactions between different parts of a system. This approach is often used in business and management to improve efficiency and effectiveness.

A contingency approach is a method of management that emphasizes the importance of adapting to changing circumstances. This approach is often used in situations where there is a lot of uncertainty or where the environment is constantly changing.

A quantitative approach is a method of management that emphasizes the use of data and statistics to make decisions. This approach is often used in situations where there is a lot of data available or where the decision-making process is complex.

A process approach is a method of management that emphasizes the importance of improving the efficiency of processes. This approach is often used in situations where there is a lot of waste or where the process is not meeting customer needs.

In conclusion, the correct answer is C. system approach. Operation research, facility layout, and MIS are all examples of systems thinking, which is a holistic approach to problem solving that considers the interactions between different parts of a system.