Which of the Following Statements Is True About Comparative Advantage

Which of the following statements is true about comparative advantage?

A) Comparative advantage exists whenever one person,firm,or nation can do something with greater opportunity costs than some other individual,firm,or nation.
B) Comparative advantage is interesting theoretically,but it is not relevant when evaluating real-world economic conditions.
C) Third-world countries cannot possibly have a comparative advantage in the production of any good or service because of the relatively low educational attainment of their work force.
D) Comparative advantage exists whenever one person,firm,or nation can do something with lesser opportunity costs than some other individual,firm,or nation.
E) Only highly advanced economies can have a comparative advantage in the production of a good or service.