Final answer:
Quantum mottle is most noticeable with low mAs and high kVp, as low mAs produces fewer X-ray photons leading to a grainier image.
Step-by-step explanation:
Quantum mottle is an artifact seen in radiographic imaging, often associated with the statistical nature of X-ray photon distribution. It is most noticeable when the number of X-ray photons reaching the detector is low, creating a grainy or spotty appearance on the image. In the context of imaging parameters, quantum mottle would probably be most noticeable when using low mAs and high kVp (option d). Low mAs means fewer X-ray photons are produced, which can contribute to increased quantum mottle, while high kVp allows for higher penetration power but doesn't necessarily increase the number of photons that reach the detector.