According to the author, which of the following was a favorite subject for American modernists

A．the development of Cubism
B．modern art movements in the United States
C．contemporary artists in the United States
D．the influence of photography on landscape painters

A．to demonstrate that photography was the major influence in modern art
B．to compare him to other artists of the time
C．to point out that many artists learned their craft by studying with him
D．to give an example of someone who had an influence on modern art