Question

Nivea wants to buy a new backpack. She looks at different choices. One store has a yellow backpack and a large blue one that she likes. Another store has a big, red backpack and a smaller red one. Nivea wants a big backpack and she chooses the bigger blue one. What is the most likely opportunity cost of her decision?

a- the money she spent on the backpack
b- the smaller red backpack
c- the yellow backpack
d- the big, red backpack

My answer is d.