Answer:
The correct answer is D,it ensures greater production to be realized than would otherwise be possible.
Explanation:
Specialization and exchange ensure that an economy devotes itself to producing goods or services that it has lower domestic opportunity costs compared to domestic opportunity costs of other nations and buys from others those goods or services it has higher domestic opportunity costs compared to others.
Option C is wrong as specialization and exchange do not eliminate opportunity costs,they only reduce them to the minimum possible.