Which of the following is not an effective way to prevent heat stress and stroke?
A. Take a 10-minute rest for every 45 minutes of activity.
B. Wear loose-fitting clothing that allows sweat to evaporate.
C. Wear a minimum of SPF 15 sunscreen.
D. Drink water before, during, and after a workout.

Investigator a has biological specimens that are coded and linked to identifiers of the source individuals. investigator a provides the specimens to investigator b but does not provide the individual identifiers. investigator b agrees not to re-identify the source individuals. is investigator b's research using the biospecimens human subjects research according to the definition of human subjects research in the federal regulations?