Why does platinum metal make a good catalytic surface for reactant molecules?
a. it causes reactant molecules to be less reactive.
b. it strengthens bonds between reactant molecules.
c. it prevents products from breaking away from the surface.
d. it holds reactant molecules in a good position for them to react.

d.It holds reactant molecules in a good position for them to react.

Catalysts are those substances which increases the rate of reaction without itself being consumed in the reaction.

Platinum metal has active sites on its surface and thus reactant molecules can be brought into closer contact with one another. If more molecules can be brought closer together, there is better chance of an effective collision and thus the rate of reaction increases and it acts as a good catalytic surface.

the mantle

explanation:

earth is divided into three layers: the crust or the outermost layer on which we live; the underlying, middle layer - the mantle - and the core (the innermost layer of earth).