If d and n are the effective depth and depth of the neutral axis respectively of a singly reinforced beam, the lever arm of the beam, is
A
d
B
n
C
$${\text{d}} + \frac{{\text{n}}}{3}$$
D
$${\text{d}} - \frac{{\text{n}}}{3}$$
Correct Answer: $${\text{d}} - \frac{{\text{n}}}{3}$$