Which type of thermal energy transfer occurs mostly in fluids?

insulation

radiation

convection

conduction

Convection - is your answer.

Explanation:

Convection is by far the most efficient and common way for heat to be transferred through liquids and gases. It occurs when some regions of a fluid get hotter than others, causing currents in the fluid that move it around to distribute that heat more evenly. That's what I found on the internet

convection