What is the situation called when there is more of a product being offered for sale than people want to buy at that price? opportunity cost surplus shortage price fixing

Let's look at the meaning of the four terms:
opportunity cost - this is a cost of an option not chosen, upon the choise of some option.

surplus - this is a situation where more goods are offered than are needed

 shortage - this is a situation where less goods are offered than are needed

price fixing   - this is an agreement between competitors to not lower a prize for a certain product.

So the correct answer is surplus!