Correct Answer: (d) (a), (b) and (c) are correct
Solution:Characteristics of air mass: Air mass refers to immense body of air with 3-D structure extending upto tropopause having relatively homogenous condition in its horizontal layer and identifiable by its vertical gradients which are Sleek. Air mass is a dynamic body of air with its own physical characteristics differentiable from surrounding with physical properties like specific humidity, lapse rate and density more or less homogenous in its different layers.