Correct option is (b) Fourier’s law
Easy explanation: Major principle behind heat sink is Fourier’s law. Fourier’s law of heat conduction, simplified to a one-dimensional form is, when there is a temperature gradient heat will be transferred from the higher temperature region to the lower temperature region. The rate at which heat is transferred by conduction is proportional to the product of the temperature gradient and the cross-sectional area through which heat is transferred.