Why does exhaling (Breathing) under water make your stroke more efficient?

Darren was recently ticketed for speeding over 110 mph on the freeway. when the police officer stopped darren and asked him why he was going so fast, he replied that he was "king of the world." the month before this, darren felt sad and listless and had trouble getting up the energy to go to school. he probably suffers from:

What is one way that vance might have been able to prevent this injury?

What are 3 important public health tools for addressing flu outbreaks and why