What does the marketing concept involve?

Select one:

a$.$ selling products at the highest prices that the market will bear with the idea of maxinging profits in the short run

b$.$ selling as much product as possible under the assumption people will buy more goods and services if aggressive selling techniques are used

c$.$ focusing on production in order to increase product quality and lower prices

d$.$ focusing on customers' wants so that the organization can distinguish its product $($or products$)$ from the competitors' products