Which of the following is a symbol for a unit of luminous intensity?

Luminous intensity is a measure of the amount of light emitted by a source in a particular direction, and it has the unit "candela," which is symbolized by "Cd." The candela is one of the seven base units in the International System of Units (SI) and specifically quantifies the intensity of light as perceived by the human eye.

The other options represent different units of measurement: "M" typically stands for meters, which is a unit of length; "Mol" is short for mole, a unit in chemistry that measures the amount of substance; and "Kg" stands for kilogram, which measures mass. Therefore, none of these options relate to the concept of luminous intensity, making "Cd" the correct choice as it is directly associated with this measurement.