SOLUTION $($ HFK $)==$ : In civil engineering, theories underpin the understanding and application of fundamental principles governing the behavior of materials and structures. These theories encompass topics such as structural analysis, soil mechanics, fluid dynamics, and construction management. They provide insights into the stresses and strains within structures, the stability of foundations, and the dynamics of fluid flow in hydraulic systems. By leveraging theoretical knowledge, civil engineers design resilient infrastructure, mitigate environmental impacts, and ensure the safety and longevity of built environments.