To avoid large centering error with very short legs, observations are generally made A. To chain pins B. By using optical system for centering the theodolite C. To a target fixed on theodolite tripod on which theodolite may be fitted easily D. All the above

The correct answer is D. All the above.

To avoid large centering error with very short legs, observations are generally made to chain pins, by using optical system for centering the theodolite, and to a target fixed on theodolite tripod on which theodolite may be fitted easily.

Chain pins are used to mark the position of the theodolite on the ground. This helps to ensure that the theodolite is centered correctly. The optical system for centering the theodolite helps to ensure that the theodolite is level. The target fixed on theodolite tripod helps to ensure that the theodolite is pointing in the correct direction.

All of these methods help to reduce the centering error and improve the accuracy of the observations.