Observation: Starch forms a translucent mixture.

Explanation:
When Rohit mixed starch with water, boiled the mixture, and stirred it, he observed that the starch formed a translucent mixture. This means that the mixture became somewhat clear, allowing light to pass through, but it was not completely transparent.

The observation can be explained by the process of gelatinization. Gelatinization is a process in which starch granules absorb water and swell, resulting in the thickening of the mixture. When starch is mixed with water and heated, the hydrogen bonds between starch molecules break, allowing water molecules to penetrate the granules. As a result, the starch granules absorb water and become swollen.

The swollen starch granules then disperse in the water, forming a colloidal suspension. This suspension scatters light, resulting in a translucent appearance. However, the mixture is not completely transparent because the starch particles are still dispersed throughout the water, causing some light scattering.

Importance of stirring:
Stirring the mixture is important to ensure that the starch granules are evenly dispersed in the water. It helps to break up any clumps and promotes the gelatinization process. Stirring also prevents the mixture from becoming lumpy and ensures a smooth and consistent texture.

Other options:
a) Starch floats on the surface of the water: This observation is not correct because starch does not float on the surface of the water. Starch particles are denser than water and tend to settle down.

b) Starch settles down at the bottom: This observation is also not correct. Starch particles do not settle down at the bottom but instead disperse throughout the water.

d) Starch forms a transparent mixture: This observation is not correct either. As explained earlier, the starch mixture becomes translucent but not completely transparent due to the scattering of light by the dispersed starch particles.

In conclusion, when starch is mixed with water, boiled, and stirred, it forms a translucent mixture due to the gelatinization process. Stirring is important to ensure uniform dispersion of starch particles in the water.