Q.

Fourier's law of heat conduction is (where Q = Amount of heat flow through the body in unit time, A = Surface area of heat flow, taken at right angles to the direction of heat flow, dT = Temperature difference on the two faces of the body, dx = Thickness of the body, through which the heat flows, taken along the direction of heat flow, and k = Thermal conductivity of the body)

• Ak. A. (dT/dx)
• Bk. A. (dx/dT)
• Ck. (dT/dx)
• Dk. (dx/dT)