the reason astronomers use large diameter telescopes...?

There are two reasons for using a large aperture, and they are related to each other. The first is to gather enough light to see dimmer objects, and the second is to provide a sufficiently large opening to minimize the effects of diffraction (based on the wavelength of visible light) in order to provide improved resolution capability. The field of view and the magnification depend on the focal lengths built into the telescope and the eyepiece being used.

The way this is worded, I think that C and D are both sort of relevant, but D is the more technically accurate response. A and B are not really appropriate.

ADDED: Technically, magnification does not depend on aperture, but only on the focal lengths mentioned above. However, realistically, the magnification of a telescope is limited by its aperture. Since true field of view is then related to its magnification, all of the answers above do depend to differing degrees on aperture. In the cases of A and B, the dependence is a limit and not a direct relation. In the case of C, the answer fails to mention resolution or diffraction limits. So - I still think D is the BEST answer. Tough question.

A is actual in that for the comparable length, an optical telescope would be a lot extra high priced than a radio one. it somewhat is because of the fact for a telescope to artwork nicely, it desires to be made to an accuracy of a fragment of the wavelength it observes. For mild, meaning precision of a few hundred nanometres is needed. Radio waves are a lot longer, so the telescope would not want something like the precision engineering. Millimetre accuracy or maybe much less will do. even with the shown fact that, the call of a telescope - how a lot element it could see - is extra effective the larger the telescope, yet much less the longer the wavelength it observes. So whilst it somewhat is decrease priced to make a great radio telescope, that telescope won't see the style of superb element a a lot smaller optical telescope ought to.

The larger the aperture, the more light the telescope can gather.

You are a complete Failure. Lazy***.