The light-gathering capacity of a telescope is dependent upon the: magnification focal length size of human iris area of aperture

The correct answer is area of aperture.

Explanation:

Telescope is an optical instrument which focuses light towards one point and makes far away things look nearer. It is made up of the arrangement of lenses or curved mirrors and lenses which focuses the light and makes the image of the object magnified.

The light-gathering capacity of a telescope is the ability to resolve small detail depends on the diameter of its objective lens. Larger the area of aperture, telescope can collect more light ans as a result, fine detail is obtained.

Hence, the correct answer is area of aperture.