What do hydrometers test?

{A}the buoyancy of water

[B} the pollutants in water

[C} the pH of water

Hello.

The answer is: A. the buoyancy of water

hydrometer is an instrument used to measure the specific gravity of liquids; that is, the ratio of the density of the liquid to the density of water, Used for measuring the relative density of liquids based on the concept of buoyancy.

Have a nice day

A the right answer, bcz

hydrometer or areometer used for measuring the relative density of liquids. it is based on concept of buoyancy of liquids.