What is the approximation made in the parallax method?
A. All distances measured between two points on earth are zero.
B. All distances measured between two points on earth are constant.
C. Distance between a point on the earth and the planet is very large as compared to the distance between two points on earth’s surface.
D. No approximation is made.

Hint :In order to answer the question, we will go through the whole concept of parallax method, as why parallax method is used. It is used to measure large distances. We will also discuss the other effects or implementation of parallax.

Complete Step By Step Answer:
In the parallax method, an approximation is made that the distance between a point on the earth and the planet is very large as compared to the distance between two points on the earth’s surface.
Parallax method is used for the measurement of planet distance and also used to measure distance of stars and planets.
To measure large distances, like the distance of a planet or a star from Earth, space experts utilize the guideline of parallax. Here, the term parallax is the semi-point of tendency between two sight-lines to the star, as seen when Earth is on the inverse sides of the Sun in its circle. These distances structure the least bar of what is classified "the vast distance stepping stool", the first in a progression of techniques by which stargazers decide the distances to heavenly articles, filling in as a reason for other distance estimations in cosmology shaping the higher rungs of the stepping stool.
Parallax additionally influences optical instruments, for example, rifle scopes, optics, magnifying lens, and twin-focal point reflex cameras that view objects from marginally various points. Numerous creatures, alongside people, have two eyes covering visual fields that utilize parallax to acquire profundity discernment; this interaction is known as stereopsis.
Hence, the correct option is (C.) Distance between a point on the earth and the planet is very large as compared to the distance between two points on earth’s surface.

Note :
A simple everyday example of parallax can be seen in the dashboard of motor vehicles that use a needle-style non-LCD speedometer gauge. When viewed from directly in front, the speed may show exactly 60, but when viewed from the passenger seat' the needle may appear to show a slightly different speed, due to the angle of viewing.