Among the following statements relating the fundamental lines of a transit theodolite, which one is CORRECT?
- The line of collimation must be perpendicular to the horizontal axis at its intersection with the vertical axis.
- The axis of altitude level must be perpendicular to the line of collimation.
- The axis of plate level must lie in a plane parallel to the vertical axis.
- The Vernier of vertical circle must read zero when the line of collimation is vertical.