The shape of a raindrop becomes spherical primarily due to surface tension; option [B]. Surface tension is the cohesive force between water molecules at the surface, causing them to pull inward. When a raindrop forms, surface tension acts equally in all directions, minimizing the surface area and pulling the drop into a spherical shape. This occurs despite the influence of gravity, which tends to deform the drop slightly. While viscosity, elasticity, and gravity play roles in the behavior of raindrops, surface tension is the dominant force determining their shape. Raindrops maintain their spherical form until they encounter air resistance or other forces that may cause deformation. Understanding the interplay between surface tension and external forces helps explain the characteristic shape of raindrops and their behavior during precipitation events.