Increasing milliamperage (mA) influences x-ray beam quantity as it causes it to:

Increasing milliamperage (mA) directly affects the quantity of x-ray photons produced during the imaging process. When mA is increased, it essentially means that more electrons are being emitted from the cathode and are available to be accelerated towards the anode. This increase in electron numbers translates to a higher number of x-ray photons being generated when these electrons interact with the anode target.

As a result, the x-ray beam becomes more intense, resulting in a greater quantity of x-rays reaching the detector or image receptor. This is significant because more photons can improve image quality by enhancing the contrast and reducing noise, assuming other factors such as exposure time and kVp remain constant.

Other options do not accurately represent the impact of mA changes on the x-ray beam's quantity. An increase in mA will never decrease, remain unaffected, or remain constant; it unequivocally leads to an increase in the x-ray photon output. Thus, understanding the relationship between mA and x-ray beam quantity is fundamental in radiographic practice to ensure optimal imaging conditions.