Aparticular milliampere-seconds value, regardless of the combination of milliamperes and time, will reproduce the same radiographic density. this is a statement of the
a. line-focus principleb. inverse-square lawc. reciprocity lawd. law of conservation of energy

C. Reciprocity law

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

this could be newton#'s law of cooling. the cooling curve is exponential

float.

archimedes' principle

denser than water sinks in water.

denser than mercury would sink in it