Which of the following represents expression for the passive earth pressure?

A

$$\tan^2 \left(45^\circ + \frac{\phi}{2}\right)$$

B

$$\frac{\mu}{1 - \mu}$$

C

$$\tan^2 \left(45^\circ - \frac{\phi}{2}\right)$$

D

$$\frac{\mu}{1 + \mu}$$