creepy uncle joe is a loser

Which of the following would a historian most likely study to find data

Mankiw attributes – chapter 1 and his 10 principles – differences in living standards within a countryover time and across countries at a moment in time to: a. the presence or absence of inflation and unemployment. b. the allocation of resources between private markets and the public sector. c. those that have dealt successfully with the efficiency v. equality tradeoff and those that haven’t. d. differences in productivity. e. ones that think at the margin and respond to incentives and those that don’t.

How does the author's discussion of schroeder's study contribute to the development of ideas about how children react to mistakes?