The opportunity cost of Maria's purchase refers to what she is giving up in order to buy the sun hat and the beach towel.
If she decides to purchase the sun hat ($8.00) and the beach towel ($7.00), she will spend a total of $15.00.
Based on the available options, the opportunity cost of purchasing the sun hat and towel is the magazines ($8.00) because she can't buy them with the remaining money, as well as the bathing suit ($15.00) because it is another item she cannot buy with her budget.
Therefore, the correct answers are:
- The magazines
- The bathing suit