task $99===$In civil engineering, foundational theories underpin the design, analysis, and implementation of infrastructure. Classical mechanics, materials science, and fluid dynamics form the theoretical bedrock for structural engineering, allowing engineers to predict how structures will behave under different loads and environmental conditions. Soil mechanics and geotechnical engineering theories inform the design of foundations and earth structures by understanding soil behavior and properties. Transportation engineering relies on traffic flow theory and network analysis to optimize road and transportation systems. Environmental engineering integrates principles of chemistry, biology, and physics to address pollution control and waste management. These theories collectively drive innovation and ensure the safety and sustainability of civil infrastructure.