Scottish-born John Grierson, who was educated in the United States during the 1920s, was impressed by:

A. the accuracy of the working-class milieus in the slapstick comedies of Chaplin and Keaton.
B. how powerfully American cinema shaped mass audiences' responses.
C. the way Hollywood cinema combined minute details with awesome scope.
D. the centralized efficiency of the studio system in Hollywood cinema.

Answer: B