Final answer:
Platinum is an expensive, silver-white metal used in jewelry and industrial processes to speed up chemical reactions.
Step-by-step explanation:
The element that matches the description of being an expensive, silver-white metal used in jewelry and also used in some industrial processes to speed up chemical reactions is platinum (option C).
Platinum is a precious metal that is known for its durability and resistance to corrosion, making it ideal for jewelry. It is also used as a catalyst in various chemical reactions due to its ability to facilitate and speed up these reactions.
For example, platinum is used in catalytic converters in automobiles to convert harmful pollutants in exhaust gases into less harmful substances.