Which of the following sentences from the section "The Limits To Free Enterprise With A Mixed Economy" BEST develops a central idea of the article? a. In addition, the government often is asked to get involved in the economy to correct situations in which the price system does not work.

b. A natural monopoly is a type of market dominance that exists due to the high startup costs of conducting a business in a specific industry.

c. The government pays much of the cost of medical care for the aged and those who live in poverty.

d. In this mixed economy, individuals can help guide the economy.