Answer:
d. People face trade-offs
Step-by-step explanation:
Since maria has 20 hours training in a week and the training consist of swimming, biking and running also she is not able to do three at the same time so for approaching these 3 different time she will engaged i.e. she trade off the time between these three things.
So, she sacrifice some time for each kind of the activity therefore the correct option is d.