task : $3\mathrm{.}20$##"What are the foundational theories in civil engineering and how do they underpin the discipline's practice? Discuss the key principles of structural mechanics, materials science, and fluid dynamics as they relate to civil engineering. Explore the significance of theories such as elasticity, plasticity, and fluid flow in designing infrastructure. Analyze how these theories inform the construction of buildings, bridges, dams, and other civil works, ensuring safety, durability, and efficiency. Furthermore, examine the role of theoretical models in predicting and mitigating structural failures and natural hazards. Finally, consider the evolving nature of civil engineering theories in response to technological advancements and environmental challenges."