<span>Heart Rate Reserve, HRR. Heart rate reserve (HRR) is the difference between resting heart rate (HR<span>rest) and maximum heart rate</span> (HRmax). Heart rate reserve is used when determining exercise heart rates. The Karvonen formula is used to calculate exercise heart rate at a given percentage training intensity.</span>
Answer:
(B) Ask for a ride home if he feels threatened by a gang member.
Explanation:
It is the most logical answer because if something where to happen he would have someone else present.