Poisson’s ratio for linear elastic, homogeneous and isotropic materials:

Correct option is A

Poisson's ratio:
The ratio of lateral strain to longitudinal strain is called Poisson's ratio
The negative sign indicates that the radius of the bar decreases when it is stretched.
Poisson's ratio is a dimensionless and a unitless quantity.
Poisson's ratio for linear elastic, homogeneous and isotropic materials remains constant throughout