Answer:
C. Reciprocity law
Step-by-step explanation:
The reciprocity law is based on the assumption that the density or blackening of a photographic film is dependent merely on the exposure or quantity of radiant energy which the film absorbs and is independent of the rate at which the energy is applied.
This law pertains to the milliampere-seconds in the sense that all combinations of milliamperes and time that amount to an equal quantity will produce the same amount of radiographic density.
The answer is:
C. Reciprocity law