Answer:
a.Attending a movie
Step-by-step explanation:
The opportunity cost is the cost or value or the item foregone. That is way opportunity cost is also known as alternative foregone.
It is also known as the real cost. When the wants are listed in a scale of preference in the order of priority, the limited resources is used to satisfy the first item on the list while the next unfulfilled want is the opportunity cost.
Therefore, for John, the opportunity cost is attending the movie, option a.