ANS:D - all (a), (b) and (c).

The correct statement is: all (a), (b), and (c). Here's why: (a) Thermal diffusivity of a material indeed has the unit m2/secm2/sec. This unit represents the rate at which heat diffuses through a material relative to its ability to store thermal energy. (b) Thermal diffusivity is defined as ρ⋅Cp​K​, where:

• K is the thermal conductivity of the material (units: W/m⋅KW/m⋅K),
• ρ is the density of the material (units: kg/m3kg/m3),
• Cp​ is the specific heat capacity of the material (units: J/kg⋅KJ/kg⋅K).

(c) Thermal diffusivity can also be expressed as the ratio of thermal conductivity to thermal capacity, which is consistent with the formula ρ⋅Cp​K​. This ratio represents how fast heat can propagate through a material relative to its ability to store heat. Therefore, all the statements (a), (b), and (c) are correct. Thermal diffusivity is indeed represented in m2/secm2/sec, defined as ρ⋅Cp​K​, and can be seen as the ratio of thermal conductivity to thermal capacity.