The correct answer is D because the iris directly controls the amount of light entering the lens, which has the most immediate effect on image brightness. When the iris opening is enlarged, more light reaches the image sensor, and the captured image becomes brighter. This makes iris adjustment the preferred action when the goal is simply to improve overall brightness. By contrast, resolution affects image detail, not light intake.
Angle of view changes scene coverage, not exposure level. Focal length changes magnification and framing, but it does not function as the primary exposure control in this context.
This aligns with the exposure-centered logic emphasized throughout the training material, where Huawei highlights advanced imaging control and notes that "T-Shot, Huawei's patented exposure technology, enables optimal imaging of targets and vehicles at the same time" and that traditional exposure methods cannot properly expose different targets in one image . In practical camera operation, brightness problems are first treated as an exposure issue, and among the listed options, the iris is the only parameter that directly regulates exposure by controlling incoming light.