The correct answer is: A. Stabilises an emulsion.
An emulsifier is a substance that stabilizes an emulsion, which is a mixture of two or more immiscible liquids, such as oil and water. Emulsifiers work by forming a layer around the droplets of one liquid, preventing them from coming into contact with each other and forming larger droplets. This layer can be made up of molecules that have both water-loving and oil-loving ends, which allows them to attach to both liquids.
Option B is incorrect because flocculation is the process of clumping together of small particles. This is the opposite of what an emulsifier does, which is to prevent particles from clumping together.
Option C is incorrect because accelerating the dispersion of an emulsion would mean breaking up the droplets of one liquid into smaller droplets. This is not what an emulsifier does, which is to stabilize the emulsion by preventing the droplets from breaking up.
Option D is incorrect because homogenizing an emulsion would mean making the emulsion more uniform. This is not what an emulsifier does, which is to stabilize the emulsion by preventing the droplets from coming into contact with each other.