Answer:
The right choice is "3 Correctly ignored a sunk cost"
Explanation:
As the ticket to the opera was already bought and it is nonrefundable, nonexchangeable, and nontransferable; whether Van decides to go to the opera or to go to the party with Amy; he has incurred $100 cost of ticket which can not be recovered in any manner.
The ticket cost in this question is categorized as sunk cost - cost that incurred in the past and will be remained the same regardless of any future actions. Thus, this type of cost should be ignored when making decision for the future.
So, "3 Correctly ignored a sunk cost" is the correct choice.