Markets,viewed from the perspective of the supply and demand model:

A) assume many buyers and many sellers of a standardized product.
B) assume market power so that buyers and sellers bargain with one another.
C) do not exist in the real-world economy.
D) are approximated by markets in which a single seller determines price.

The supply and demand model assumes many buyers and many sellers of a standardized product, which is a characteristic of competitive markets in the real-world economy. The model is a simplified representation of how competitive markets function, and it is used to understand how changes in factors such as price, supply, and demand affect market outcomes. Option B is incorrect because the supply and demand model assumes that no one party has market power, which means that buyers and sellers cannot bargain with one another. Option C is incorrect because markets do exist in the real-world economy. Option D is incorrect because a single seller determining the price is a characteristic of a monopoly, which is not described by the supply and demand model.