Based on the excerpt from "Dusk," the best inference about Gortsby’s character based on his choices is:
He can admit failure.
This inference is supported by the text, which indicates that Gortsby feels he has failed in a "more subtle ambition" and is "heartsore and disillusionised." It suggests a level of self-awareness and acceptance of his circumstances, indicating that he acknowledges his failures rather than pretending to be part of the world of prosperity and success he observes around him.