The correct option is (b) Gradient of entropy and vorticity
Explanation: According to the Crocco’s theorem, there is a relationship established between vorticity, gradient of enthalpy and gradient of entropy.
V × (∇ × V) = ∇h0 – T∇s
Where, ∇ × V is the vorticity
∇h0 is gradient of total enthalpy
T∇s is gradient of entropy