Which factor will produce the least receptor exposure?

The answer is correct because it reflects the principle of radiation exposure in imaging. Receptor exposure is determined by several factors, primarily the milliampere-seconds (mAs), which is the product of the tube current (mA) and exposure time (seconds).

In this case, the fourth choice has a combination of low mA and a relatively shorter exposure time, leading to the lowest mAs among the options presented. Specifically, 100 mA multiplied by 0.020 seconds yields 2 mAs.

Additionally, the kV (kilovoltage) influences the quality, penetration, and quantity of the radiation produced, but in this scenario, the substantial drop in mAs (due to the combination of lower mA and seconds) is the primary reason for the decreased receptor exposure. The other options have higher or comparable mAs values, resulting in greater receptor exposure overall.