What type of muscle fibers can maintain low-intensity muscular activities for prolonged periods of time?

a. fast twitch
b. medium twitch
c. slow twitch
d. anaerobic twitch

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?