Answer:
False
Step-by-step explanation:
The opportunity cost refers to the benefit that is foregone by choosing some other alternative. It is measurable in monetary terms as well as in non-monetary terms.
In our case,
Monica paid for CD = $12
Hence, she already paid for the CD, so here the opportunity cost is either she keep the CD or she not keep the CD for the amount of $18.
Hence, if Monica decided to keep the CD then the opportunity cost of keeping the CD is $18.