Which of the following defines demand?

Question $7$ options:

a$)$

The quantity of a product offered to the market by a supplier at various prices for a specified period

b$)$

A company's product sales as a percentage of total sales for that industry

c$)$

The quantity of a product that could be sold in the market at various prices for a specified period

d$)$

A part of profit percentage that is given up in exchange for acquiring a good or service