Reducing the intensity of light using the iris diaphragm or staining a specimen can improve multiple choice contrast reflection magnification incorrect resolving power

The answer is contrast.

Iris diaphragm is the circular object in front of the lens of the eye. Iris could block some light that come to the eye. If the muscle around it contract, the iris will block more light. If there is less light inside the eye, the signal sent to the brain will create a picture with more contrast. Magnification and focus should be regulated by the lens.

the answer would be knowledge about cars!