Which of the following properties of water can be used to explain the…

Surface tension is the property of a liquid's free surface that makes it behave like a stretched elastic membrane: unequal intermolecular attractive forces on surface molecules (pulled inward by the bulk liquid, with no equivalent pull from above) create a net inward force that minimizes the surface's area for a given enclosed volume. Among all possible shapes, a sphere has the smallest surface area for a given volume, so a liquid mass left to itself under surface tension alone tends toward a sphere.

A falling raindrop is small enough that surface tension (acting to minimize its surface energy) dominates over gravity and air-drag distortion, so it settles into (very nearly) a spherical shape, matching the saved answer, surface tension. Very large drops flatten slightly at the base from air resistance, but the rounding itself is still governed by surface tension.

This rules out the other properties:

• Viscosity measures a fluid's resistance to flow/shear (how fast it deforms), not the equilibrium outer shape a drop settles into.

• Critical phenomenon describes how the liquid and vapour phases merge near a substance's critical temperature/pressure, unrelated to ordinary droplet geometry.

• Pressure: the extra internal pressure inside a curved drop (Laplace's law, delta-P = 2T/r) is itself a CONSEQUENCE of surface tension, not an independent cause of the spherical shape.