The correct option is A Dissolved salt
Dissolved salts is not an essential part of an emulsion. Emulsion, a mixture of two liquids that ordinarily do not combine, such as oil and water. When stirred or shaken vigorously, the two liquids will form a temporary emulsion. Within a relatively short time, however, the two will separate into distinct layers. A permanent emulsion can be made by adding a third substance, called an emulsifier or emulsifying agent, to the mixture. Oil and water will form a permanent emulsion if soap or detergent is added as an emulsifier. Milk is a permanent emulsion of butterfat in water, with casein acting as the emulsifier. An emulsion is a colloid.