Final answer:
d. The cost of making spaceships
The opportunity cost of making a robot in Nevarro is the cost of making spaceships.
Step-by-step explanation:
The opportunity cost of making a robot in Nevarro is the cost of making spaceships. Opportunity cost refers to the value of the next best alternative that is forgone when making a decision. In this case, if Nevarro chooses to make robots instead of spaceships, they would have to give up the production of spaceships, resulting in a loss of 4,000 spaceships per year.