Please explain the following 23rd question with reason.

Dear Student,
23.
The current density of conductor is given by:
J = nev_d
where v_d = drift velocity 
Also, 
v_d = eEτ/m
where, E = electric field 
Hence,
J = ne²Eτ/m
J = σE
(where σ = ne²τ/m)
it is electrical conductivity
so, 
σ = J/E 
Hence, the ratio of electric field and the current density at a point is called conductivity (option b).
Regards