Answer:
D
Step-by-step explanation:
Maria's time (resource) is limited so she has to choose between activities. This is known as trade off. Due to unlimited wants and limited resources available to fulfil the needs, humans must choose between activities.
This concept of trade off also gives rise to opportunity cost
opportunity cost is the cost of the next best option forgone when one alternative is chosen over other alternatives
If Maria swims, she forgoes the opportunity to go bike riding or running