Which one of the following statements is true with regard to an economy which is on its production possibility frontier?

• A. The economy has to sacrifice some production of one commodity in order to increase the production of another commodity
• B. There is no limit or constraint for the economy in the production of goods and services
• C. The economy can produce more than one commodity up to a point without reducing the production of any other commodity
• D. Its production possibility frontier is an upward sloping curve