Answer:

Introduction:
Theodolite is an essential instrument used in surveying for measuring horizontal and vertical angles. The final setting of the plates of theodolite when taking a foresight is an important step in the surveying process. In this response, we will discuss the correct setting of the plates of theodolite when taking a foresight.

The Final Setting of the Plates:
The final setting of the plates of theodolite when taking a foresight is achieved by using the upper clamp screw. This screw is responsible for holding the upper plate in place. The upper plate is the one that contains the telescope and the vertical circle. The upper clamp screw is used to clamp the upper plate in place after the desired angle has been set.

Explanation:
When taking a foresight, the telescope of theodolite is pointed towards the object whose angle is to be measured. The vertical circle is then rotated until the cross-hairs of the telescope coincide with the object. At this point, the desired angle is set and the upper clamp screw is tightened to hold the upper plate in place. The lower clamp screw is not used in this process as it is responsible for holding the lower plate in place.

The upper tangent screw is used to make fine adjustments to the vertical circle. It is used to bring the cross-hairs of the telescope into exact coincidence with the object being measured. The lower tangent screw is used to make fine adjustments to the horizontal circle. It is used to bring the cross-hairs of the telescope into exact coincidence with the vertical axis of the instrument.

Conclusion:
In conclusion, the final setting of the plates of theodolite when taking a foresight is achieved by using the upper clamp screw. This screw is responsible for holding the upper plate in place after the desired angle has been set. The upper tangent screw is used to make fine adjustments to the vertical circle, and the lower tangent screw is used to make fine adjustments to the horizontal circle.