Q1: Pick up the correct statement from the following :

ANS:A - the eyepiece plays no part in defining the line of sight

Line of Sight: It is line passing through the cross hair and optical centre of objective lens. However Eyepiece only clarifies the cross hair in diaphragm. Thus Eye piece plays no important role in defining the line of sight. Diaphragm, optical centre are part of the telescope and those are very important to observe the line of sight. According to D V GUPTA survey book. He says that line of sight is the line which passes through the optical centers of both glasses i.e. eyepiece & object glass towards the object. The line passing through Centre of cross hair and objective lense to cross staff called a line of sight. No matter of eye-piece. Passing through the intersection of crosshairs diaphragms and the optical center of object glass and its continuation. Axis of Telescope - Eyepiece to Optical.
Line of Sight - Diaphragm to Optical.