Question

Which of the following forms a colloidal solution in water?
A.Starch
B.Glucose
C.Urea
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Answer 1

Colloidal solution generally refers to the overall mixture, so that means, a colloidal solution is a solution where the colloid mixes uniformly. Also, the colloidal solutions can be identified using the Tyndall Effect.

Complete answer:
Colloids (can even be known as colloidal solutions or colloidal systems) are basically the mixtures in which particles of one substance which are microscopically dispersed insoluble, are suspended in the other substance. Some examples of colloids are Fog, sprays, milk and mayonnaise, starch etc.
A mixture can be classified as a colloid if it's suspended particles do not settle (in the way that the particles of suspensions settle at the end of the container if it is not disturbed). Colloidal solutions are also known to have the Tyndall Effect, which can be defined as a phenomenon where the beams of light that incidents on colloids get scattered due to its interaction happening between the colloidal particles and the light.
In very simple words, we can say that the colloids are a mixture in which one of the substances gets split down into very minute particles which are dispersed throughout a second substance. The minute particles present here, are known as the colloidal particles.
The molecules of starch have colloidal dimensions. That implies, starch is the substance that, in water it will form a colloidal solution.
So, option (a) is correct.

Note:
Colloidal systems can take place in any of the three states of matter such as gas, liquid or solid. The most important feature used to distinguish between a true solution and a colloidal solution is the dimensions of the constituent parts.