The opportunity cost is the value of the next best alternative foregone. Every decision necessarily means giving up other options, which all have a value. The opportunity cost is the value one could have derived from using the same resources another way, though this is not always easily quantifiable.
Taking an educated guess here -- I think it would be 1, 3, and 4 which all seem pretty reasonable.
Thank you for your statement, really helped me!
B is most likely the answer double check to be sure