Although expensive, platinum is used as a catalyst to break down harmful gases in car exhaust into less harmful gases. which statement best describes platinum in this use?

a. it is a homogeneous catalyst, so only a small amount is needed even though it exits with the products.

b. it is a heterogeneous catalyst, so only a small amount is needed and it is easily separated from the products.

c. it is a homogeneous catalyst, so although a large amount is needed, it is easily separated from the products.

d. it is a heterogeneous catalyst, so a large amount is needed and it exits with the products.