Answer:
The correct answer is letter "C": the value of attending the class he decided to miss.
Step-by-step explanation:
Opportunity cost reflects the benefit of the option chosen -out of different variables- compared to the benefit that could have been obtained if another option was taken. It is the return of the option taken in reference to the option forgone. Opportunity cost could be positive or negative.
In Tim's case, as he decides to stay at home because of his stomachache, he will be missing class. Thus, the class missed is Tim's opportunity cost over sleeping in.