Right choice is (b) \(∈_h=\frac{1}{E} [σ_h-μ(σ_h-σ_v)]\)
For explanation I would say: The lateral strain ∈h in the horizontal direction is given by,
\(∈_h=\frac{1}{E} [σ_h-μ(σ_h-σ_v )],\)
where, σh =horizontal stress
σv =vertical stress
E=elastic modulus
μ= Poisson’s ratio.