Which of the following is true of pathogens?
a. pathogens cause noninfectious diseases.
b. pathogens are not spread from person to person.
c. pathogens are larger organisms such as plants and animals.
d. pathogens can be found in saliva and mucus drops from sneezes.

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?