Answer:
The correct answer is option a.
Step-by-step explanation:
Opportunity cost can be defined as the cost of giving up or sacrificing the second-best alternative. In other words, it is the benefit that could have been earned if the alternative was not sacrificed.
Here, Joe bought gold coins for $1,000 and sold them at the same price. He could have instead invested in a certificate of deposit and earned a 3% interest rate. So here the opportunity cost of purchasing the gold coins is the interest earnings sacrificed.