Introduction:
In the Mechanical Engineering Optional Subject, there are several topics that require knowledge of engineering design principles. These topics are important for understanding the fundamental concepts and principles of mechanical engineering design. In this response, we will discuss some specific topics that require knowledge of engineering design principles.

1. Machine Design:
Machine design is a crucial aspect of mechanical engineering, and it involves the application of engineering principles to design various machine components and systems. Knowledge of engineering design principles is essential in machine design, as it helps in understanding the concepts of stress analysis, material selection, fatigue and fracture analysis, and design optimization.

2. Manufacturing Processes:
Manufacturing processes play a significant role in the production of mechanical components. Understanding the principles of engineering design is crucial in selecting appropriate manufacturing processes for different components. It helps in ensuring the manufacturability, functionality, and quality of the final product.

3. Finite Element Analysis:
Finite Element Analysis (FEA) is a numerical method used to analyze the behavior of structures and components under different loading conditions. Knowledge of engineering design principles is essential in FEA, as it helps in understanding the concepts of meshing, boundary conditions, material properties, and interpretation of analysis results.

4. Thermodynamics and Heat Transfer:
Thermodynamics and heat transfer are fundamental topics in mechanical engineering. Knowledge of engineering design principles is required in these subjects to analyze and design various thermal systems, such as power plants, refrigeration systems, and heat exchangers. It helps in understanding concepts like heat transfer modes, energy conversion, and system optimization.

5. Fluid Mechanics:
Fluid mechanics is another important subject that requires knowledge of engineering design principles. It helps in understanding the behavior of fluids and designing systems like pumps, turbines, and pipelines. Knowledge of engineering design principles is necessary to analyze fluid flow, pressure drop, and design efficient fluid systems.

Conclusion:
In conclusion, several topics in the Mechanical Engineering Optional Subject require knowledge of engineering design principles. These topics include machine design, manufacturing processes, finite element analysis, thermodynamics and heat transfer, and fluid mechanics. Understanding these principles is crucial for designing and analyzing various mechanical components and systems.