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.
It is measured with a barometer
<h2>Let us study about it .</h2>
Explanation:
Evaporation
It is the process of converting liquid into vapors .
Condensation
It is the process of converting vapors back into liquid state .
- Suppose if we have a sealed container and we are supplying it with no or little heat , we will see that as we increase heat , the particles starts moving faster .
- When they move they also colloide and transfer energies .
- The kinetic energies of certain molecule increase to an extent that they leave the other particles and escape in atmosphere .
- That is evaporation occurs .At the same time when these vapors collide with each other or with the walls of container they get cooled and again get converted to liquid state .
It is seen that a equilibrium is reached when "rate of evaporation becomes equal to rate of condensation ".
False
The adjective corrosive means it will definitely harm the skin
