Final answer:
To maintain the same radiographic density when the exposure time is reduced, we need to adjust the milliamperage accordingly. Therefore, the milliamperage selection that would most closely approximate the original radiographic density is 700 mA.
Step-by-step explanation:
The original exposure was made using 300 mA and 50 ms. The product of mA and ms is known as the mAs, which represents the total radiation exposure. To maintain the same radiographic density when the exposure time is changed to 22 ms, we need to adjust the milliamperage (mA) accordingly. Since the exposure time is reduced by about half, we need to increase the milliamperage by about double to compensate. Therefore, the milliamperage selection that would most closely approximate the original radiographic density is 700 mA.