【单选题】In the early 1950s,historians who studied pre-industrial Europe (which we may define here as Europe in the period from roughly 1300 to 1800) began, for the first time in large numbers, to investigate ...
A.
They had new findings.
B.
They expanded the period defined as pre-industrial Europe.
C.
They investigated the common people who took up the majority of the population.
D.
The investigations were on the kings, generals ,judges, nobles, bishops, and local magnates.