Correct Option: A

A telescope assists the eye chiefly in two way by enlarging the visual angle under which a distant object is seen, and thus magnifying that object; and, secondly, by collecting, and conveying to the eye, a larger beam of light than would enter the naked organ, thus rendering objects distinct and visible which would otherwise be indistinct and or invisible. It’s essential parts are the object glass, or concave mirror, which collects the beam of light, and forms an image of the object, and the eyeglass, which is a microscope, by which the image is magnified. Terrestrial telescope is a telescope whose eyepiece has one or two lenses more than the astronomical, for the purpose of inverting the image and exhibiting objects erect. The terrestrial telescope is also known as the spyglass.