D. terror. This is the correct option.
Harker, the lawyer, is arriving at Dracula's castle for the first time. He is really scared. He has not expected this. However, he was given some warnings because he was travelling on the eve of St. George’s Day. The mood of terror is created by these elements: the sound of wolves howling; the horses looking terrified; the phrase " the living ring of terror"; the fact that the narrator , Harker, felt fear and he could not speak or move ; and his notion of time was endeless.
These options are wrong:
A. suspense. The writer describes the feelings of Herker's. The writer has not developed the events to make the reader expect new surprising actions in this excerpt.
B. frustration . The writer describes the narrator's state of fear not his state of frustration.In spite of Herker's fear, he can get to the castle.
C. optimism. The language the writer uses is the language of terror. There is not any optimistic expression .