Which of the following chemicals is useful in photography?

Aluminium hydroxide
Potassium nitrate
Silver bromide
Sodium chloride

The correct answer is C. Silver bromide.

Aluminium hydroxide is a white, odorless, tasteless powder that is used in a variety of applications, including as an antacid, a laxative, and a component of some cosmetics.

Potassium nitrate is a white, crystalline solid that is used in a variety of applications, including as a fertilizer, a food additive, and a component of gunpowder.

Sodium chloride is a white, crystalline solid that is used in a variety of applications, including as a food additive, a water softener, and a component of table salt.

Silver bromide is a white, crystalline solid that is used in photography. It is a light-sensitive compound that is used to create the latent image on photographic film. When exposed to light, silver bromide molecules are converted into silver atoms, which form the image on the film.

The other options are not useful in photography.