Flooding is primarily caused by which of the following factors?

Answer: B — Heavy rainfall and runoff

Flooding is primarily caused by heavy rainfall and runoff. This phenomenon occurs when an excess of rainfall exceeds the ground's capacity to absorb water, leading to an overflow of rivers, streams, and other bodies of water. Factors such as soil saturation, the intensity and duration of rainfall, and the topography of the land can significantly contribute to how runoff accumulates and floods occur. Heavy rainfall events can lead to rapid inundation, particularly in urban areas where impervious surfaces like concrete prevent water absorption. Additionally, when heavy rainfall coincides with existing water levels in rivers and lakes, it can exacerbate the flooding situation. While infrastructure failure, earthquake activity, and siltation in rivers can contribute to flooding or worsen its effects, they are not the primary causes. Infrastructure failure may result in localized flooding due to broken pipes or dams, earthquakes can trigger landslides that may block rivers and cause water to back up, and siltation can affect the capacity of waterways but are secondary factors compared to the immediate effect of heavy rainfall and runoff.