Fluid motion in the natural convection heat transfer between a solid surface and a fluid in contact with it, results from the

Answer: Option B

In natural convection heat transfer, fluid motion is driven by the temperature gradient produced due to density difference. As a fluid near a heated surface becomes warmer, it tends to rise due to a decrease in density. Conversely, the cooler fluid descends. This creates a continuous circulation known as natural convection currents.

Therefore, the correct answer is Option B: Temperature gradient produced due to density difference.