Correct choice is (a) \(T_v=\frac{C_{vz} t}{H^2} \)
Easiest explanation: The time factor Tv for the vertical flow is given by,
\(T_v=\frac{C_{vz} t}{H^2}, \)
Where Cvz is the coefficient of consolidation in z-direction
t=elapsed time
H=average drainage path.