The R.L. of the point ' A ' which is on floor is 100 m and back sight reading on 'A' is 2.445 m. If the foresight reading on the point 'B' which is on ceiling is 2.745 m, the R.L. of point ' B ' will be-

Correct option is D

$$\text{Since the staff at the elevated point B on the ceiling is held vertically inverted,} \\[10pt]RL_{B} = RL_{A} + B.S._{A} + F.S._{B} \\[10pt]RL_{B} = 100 + 2.455 + 2.745 \\[10pt]\mathbf{RL_{B} = 105.20 \, m}$$​​