Consider two metal plates pressed against each other. Other things being equal, which of the measures below will cause the thermal contact resistance to increase?
(a) Cleaning the surfaces to make them shinier.
(b) Pressing the plates against each other with a greater force.
(c) Filling the gap with a conducting fluid.
(d) Using softer metals.
(e) Coating the contact surfaces with a thin layer of soft metal such as tin.