After fixing the plane table to the tripod, the main operations which are needed at each plane table station are (i) Levelling (ii) Orientation (iii) Centering The correct sequence of these operations is A. (i), (ii), (iii) B. (i), (iii), (ii) C. (iii), (i), (ii) D. (ii), (iii), (i)

The correct answer is (i), (ii), (iii).

The first step is to level the plane table. This is done by using the three leveling screws on the base of the table. Once the table is level, the next step is to orient the table. This is done by using the compass to align the north arrow on the table with the true north. Once the table is oriented, the final step is to center the table over the point that you want to survey. This is done by using the plumb bob to align the center of the table with the point.

Here is a brief explanation of each option:

(i) Levelling: The plane table must be level in order to take accurate measurements. The three leveling screws on the base of the table can be used to adjust the level.
(ii) Orientation: The plane table must be oriented in order to take accurate measurements. The compass can be used to align the north arrow on the table with the true north.
(iii) Centering: The plane table must be centered over the point that you want to survey. The plumb bob can be used to align the center of the table with the point.