99.345 m
100.345 m
100.655 m
101.870 m
Answer is Right!
Answer is Wrong!
The correct answer is $\boxed{\text{B. 100.345 m}}$.
The R.L. of a B.M. is the reference level from which all other elevations are measured. The back-sight is the distance from the instrument to the B.M., and the foresight is the distance from the instrument to the forward station. The R.L. of the forward station can be calculated by subtracting the back-sight from the foresight and
adding the R.L. of the B.M.:R.L. of forward station = R.L. of B.M. – back-sight + foresight
In this case, the R.L. of the B.M. is 100.00 m, the back-sight is 1.215 m, and the foresight is 1.870 m. Therefore, the R.L. of the forward station is:
R.L. of forward station = 100.00 m – 1.215 m + 1.870 m = 100.345 m