Molar conductivity of a solution is represented by the symbol 'λ' (lambda). It is a measure of the ability of a solution to conduct electricity. Molar conductivity is defined as the conductivity of a solution containing one mole of solute dissolved in one liter of solution, and it is usually expressed in units of Siemens per meter square per mole (S m² mol⁻¹).

Molar conductivity represents the conductivity of ions in a solution, as ions are responsible for the flow of electric current. When an ionic compound dissolves in a solvent, it dissociates into its constituent ions, which are responsible for the electrical conductivity of the solution. Molar conductivity takes into account the concentration of the ions in the solution, as well as their ability to carry electric charge.

The molar conductivity of a solution can be determined experimentally by measuring the electrical conductivity of the solution at different concentrations. By plotting the conductivity values against the square root of the concentration, a straight line is obtained. The slope of this line gives the molar conductivity of the solution.

Now, let's discuss the options given in the question:

a) A m: This option represents the molar conductivity of a solution and is the correct answer. It is the standard symbol used to represent molar conductivity.

b) mb: This option does not represent molar conductivity. The symbol 'mb' is not commonly used in scientific literature for this purpose.

c) : This option does not represent molar conductivity. The symbol 'c' is commonly used to represent concentration, but it does not specifically represent molar conductivity.

d) K: This option does not represent molar conductivity. The symbol 'K' is commonly used to represent equilibrium constants or rate constants in chemical reactions, but it is not used to represent molar conductivity.

In conclusion, the correct symbol to represent molar conductivity of a solution is 'A m' (option A). Molar conductivity is an important parameter in studying the conductivity of electrolytic solutions and understanding the behavior of ions in solution.