Why is understanding contour lines important in highway construction?

Answer: B — They help in determining proper drainage

Understanding contour lines is essential in highway construction primarily because they help in determining proper drainage. Contour lines represent the elevation and the land's slope on a topographic map. By analyzing these lines, engineers and construction professionals can identify areas where water will naturally flow, which is crucial for designing effective drainage systems. Proper drainage is vital to maintain the integrity of the roadway, prevent water accumulation, and minimize erosion, which can lead to structural issues. In the context of highway construction, it is necessary for planners to ensure that drainage systems are integrated into the design from the outset, utilizing the knowledge gained from contour line analysis to direct water appropriately and avoid future complications. The absence of effective drainage can lead to hazardous conditions and increased maintenance costs over time. Thus, the correct answer highlights the importance of contour lines in promoting safe and durable highway infrastructure through effective water management.