Answer: (3) ppm
Explanation: Concentration is defined as the amount of solute dissolved in a known amount of the solvent or a solution.
Parts per million (ppm) is used to express the concentration when a very small quantity of solute is present in a large quantity of the solution. It is defined as the mass of solute present in one milion parts by mass of the solution.
L/s is used to express flow rate.
J/g is used to express energy per unit mass.
kPa is used to express pressure.