Which variable primarily affects the amount of x-ray exposure a patient receives during an examination?

The amount of x-ray exposure a patient receives during an examination is primarily affected by exposure time. This is because the longer the x-ray beam is allowed to interact with the patient, the greater the total dose of radiation that will reach the patient's tissues. Increasing exposure time allows more photons to be emitted and ultimately increases the radiation exposure to the patient.

While other factors such as source-to-image distance, target angle, and the patient's age can influence the overall quality of the image or the specific technique parameters used, they do not have as direct an impact on the total radiation dose received as exposure time does. The source-to-image distance does play a role in the intensity of radiation at the image receptor, but exposure time is the more direct variable affecting the patient's exposure during the procedure.