In a theodolite

ANS:D - all the above.

1. The telescope axis is perpendicular to the transit axis: In a theodolite, the telescope is mounted so that its axis of rotation is perpendicular to the transit axis. This arrangement allows the telescope to rotate horizontally (in azimuth) around the transit axis while maintaining its perpendicular orientation.
2. The axis of rotation is perpendicular to the transit axis: The axis of rotation refers to the line around which the telescope rotates horizontally (azimuth). This axis is indeed perpendicular to the transit axis, allowing the telescope to rotate smoothly and accurately around the horizontal plane.
3. The telescope axis, the transit axis, and the rotation axis pass through the center of the theodolite: The theodolite is designed so that the telescope axis, the transit axis (vertical axis), and the axis of rotation intersect at the center of the theodolite. This central alignment ensures that the instrument operates accurately and consistently, allowing precise measurements of horizontal and vertical angles.