A) Identify ONE environmental factor, alluded to by the author, that is typically present and required for the spread of infectious disease on an epidemic or pandemic scale. b) Identify ONE specific example of a 20th-century health epidemic that encouraged technological advancement and that is NOT explicitly referenced by the author.

c) Explain ONE specific example of why the optimism of Sir Frank Macfarlane Burnet and George Marshall may have been misplaced.