Who exerts the single most important influence on literary naturalism, of which Theodore Dreiser and Jack London are among the best representative writers?

A、<span style="font-size: 16px;font-family: &#39;Times New Roman&#39;, serif">Freud&nbsp; &nbsp;</span>

B、<span style="font-size: 16px;font-family: &#39;Times New Roman&#39;, serif">Darwin&nbsp;</span>

C、<span style="font-size: 16px;font-family: &#39;Times New Roman&#39;, serif">W. D. Howells&nbsp;&nbsp;</span>

D、<span style="font-size: 16px;font-family: &#39;Times New Roman&#39;, serif">Emerson</span>