Which of the following factors affects both the quantity and quality of the primary beam?

Kilovoltage (kV) significantly affects both the quantity and quality of the primary beam in radiographic imaging. When kV is increased, the energy of the x-ray photons generated also increases, which enhances the penetrating power of the beam. This results in improved quality, as the higher-energy photons can traverse denser body tissues more effectively, leading to better images with higher contrast.

Additionally, an increase in kV can also lead to an increase in the quantity of x-ray photons produced since more photons are generated at higher energy levels. This increase in quantity allows for greater signal strength, which can improve image quality but may also lead to a higher radiation dose if not properly managed.

While milliamperage (mA) affects the quantity of x-rays produced by controlling the current flowing through the x-ray tube, it does not directly influence the quality or energy of the x-rays. Half-value layer (HVL) is a measure of beam quality but does not itself affect the beam's quantity; it reflects how effectively the beam can penetrate matter. Therefore, while these factors are important in radiographic imaging, kV uniquely influences both the number and energy of the primary beam, making it the primary factor in this context.