to support the main part of the instrument
to attach the theodolite to the tripod
to provide a means for leveling the theodolite
none of the above
Answer is Right!
Answer is Wrong!
The correct answer is A. to support the main part of the instrument.
The levelling head is a component of a theodolite that is used to level the instrument. It consists of a circular plate with three leveling screws, which are used to adjust the height of the theodolite until it is level. The levelling head is attached to the tripod, and the theodolite is then placed on top of the levelling head.
The levelling head does not support the main part of the instrument. The tripod does this. The levelling head is only used to level the instrument.