Which statement best describes how the author establishes mood in the excerpt?

The whole question:

Read the excerpt from The Strange Case of Dr. Jekyll and Mr. Hyde.

It was already bad enough when the name was but a name of which he could learn no more. It was worse when it began to be clothed upon with detestable attributes; and out of the shifting, insubstantial mists that had so long baffled his eye, there leaped up the sudden, definite presentment of a fiend.

"I thought it was madness," he said, as he replaced the obnoxious paper in the safe, "and now I begin to fear it is disgrace."

With that he blew out his candle, put on a greatcoat, and set forth in the direction of Cavendish Square, that citadel of medicine, where his friend, the great Dr. Lanyon, had his house and received his crowding patients. "If anyone knows, it will be Lanyon," he had thought.

Which statement best describes how the author establishes mood in the excerpt?

The answer is A.