The amounts of mood-elevating chemicals in the brain are

a. higher in sedentary people than in those who are physically active.
b. lower in sedentary people than in those who are physically active.
c. the same in sedentary people and in those who are physically active.
d. nonexistent in sedentary people but not in those who are physically active.

The question is asking us the following: The amounts of mood-elevating chemicals in the brain are... Mood-elevating means "mood-improving". Here it can help you to know that doing fitness and being physically active is good for mental health, so people who are physically active would have higher levels of those chemicals: the answer is: B. lower in sedentary people than in those who are physically active.