A colloidal system in which liquid is a dispersed phase and solid is dispersion medium is classified as –
A. Gel
B. Sol
C. Emulsion
D. Aerosol

Hint: When a substance is microscopically dispersed soluble and insoluble particles are suspended throughout another substance, this phase separated mixture is known as colloid in chemistry. Colloid is a dispersed substance, dispersed over the dispersion medium.

Complete Step by step answer:
A colloid is one of the three primary types of mixtures, one is solution and other is suspension.
A colloid is a mixture that has particles ranging between $ 1 - 1000nm $ in diameter, yet is evenly distributed through the solution. These are also called colloidal dispersions because the substance remains dispersed and does not settle to the bottom of the container.

The substance being dispersed is called a dispersed phase and the substance in which it is dispersed is the dispersion medium. For the mixture to be colloid, the substance in the dispersed phase must be larger than the size of the molecule but smaller than can be seen by naked eyes.
For solution, the particle size should be less than $ 1nm $ and for suspension particle size should be more than $ 1000nm $.
Classification of colloids- it is based on the phase of dispersed substance and the dispersion medium. For example if liquid is dispersed over gas then it is called liquid aerosol. And if the solid is dispersed over gas then it is called a solid aerosol.
Similarly, if gas is dispersed over liquid, it’s called foam. Liquid is dispersed over liquid; it's called emulsion. Solid is dispersed over liquid; it is called sol.
If gas is dispersed over solid it is called solid foam. If liquid is dispersed over solid then it is called gel and solid dispersed over solid is known as solid sol.
Here in the question, we have asked that liquid is dispersed over solid. And that colloid mixture is called gel.

So the correct option will be A.

Note: Some examples of gel are agar, gelatin, jelly etc. Some examples of sol are pigmented ink, sediment precipitates etc. Some examples of emulsion are milk, hand creams etc. examples of liquid aerosol are fog, clouds, hair sprays etc. examples of solid aerosol are smoke, ice clouds etc.