The correct option is **C. Cohesive force**. ### Detailed Explanation: 1. **Understanding the Concept of Surface Tension**: - A liquid droplet maintains its shape primarily due to a phenomenon known as surface tension. Surface tension arises from the cohesive forces between the molecules of the liquid. These forces are the attractive interactions that occur between like molecules (in this case, liquid molecules). 2. **Cohesive Forces**: - Cohesive forces are the intermolecular forces that hold the molecules of a liquid together. In a droplet, each molecule is attracted to its neighboring molecules. This attraction pulls the molecules toward each other, creating a sort of "skin" on the surface of the droplet. The result is that the droplet tries to minimize its surface area to reduce the energy associated with the surface tension. 3. **Minimizing Surface Area**: - The shape that minimizes surface area for a given volume is a sphere. Therefore, a liquid droplet naturally forms a spherical shape because this shape allows the cohesive forces to act uniformly across the surface, effectively minimizing the surface area and thus the energy of the system. 4. **Why Other Options Are Incorrect**: - **A. Gravitational force**: While gravity does act on the droplet, it does not play a primary role in maintaining the droplet's shape. Instead, gravity can cause the droplet to deform if it is large enough, leading to a more ellipsoidal shape rather than a perfect sphere. Thus, gravitational force is not the primary reason for the droplet's shape. - **B. Adhesive force**: Adhesive forces are the attractive forces between different substances (e.g., between the liquid and the surface it is on). While adhesive forces can influence how a droplet interacts with surfaces (like spreading out on a surface), they do not primarily determine the shape of the droplet itself. Therefore, adhesive forces are not the main reason for the droplet's shape. - **D. Centrifugal force**: Centrifugal force is a perceived force that acts outward on a mass moving in a circular path and is not a fundamental force acting on the droplet in a stationary context. It does not contribute to the droplet's shape or surface area minimization. ### Summary of Key Points: - **Cohesive forces** between liquid molecules are responsible for the droplet's shape. - Surface tension, resulting from these cohesive forces, minimizes the surface area of the droplet. - The spherical shape is the most efficient form for minimizing surface area for a given volume. - Gravitational and adhesive forces do not primarily dictate the droplet's shape, and centrifugal force is irrelevant in this context. ### Revision Summary: - The primary force maintaining a liquid droplet's shape is **cohesive force**. - Surface tension arises from cohesive forces, leading to a minimized surface area. - A droplet naturally forms a **sphere** to reduce energy. - Gravitational, adhesive, and centrifugal forces do not primarily influence the droplet's shape.