Which of the following factors affects the exposure time needed for adequate imaging?

The exposure time needed for adequate imaging is influenced by both source-image receptor distance (SID) and filtration, making the combined choice the correct one.

Source-image receptor distance is crucial because it affects the intensity of radiation that reaches the imaging receptor. As the distance increases, the intensity of radiation decreases due to the inverse-square law, meaning that a longer exposure time would be necessary to achieve adequate image brightness and detail at a greater distance.

Filtration, on the other hand, refers to the use of materials that absorb low-energy photons from the x-ray beam, which enhances image quality and reduces patient dose. However, increased filtration can also reduce the overall quantity of radiation reaching the receptor, thereby requiring an adjustment in exposure time; typically longer exposure times are needed to compensate for this reduction.

Combining these two principles, it's clear that both SID and filtration significantly contribute to the adjustments needed for optimal exposure times in imaging, making the answer that includes both factors the most comprehensive and correct.