A group of senators stabbed Caesar
The mood is peaceful and serene yet with a tinge of loneliness and darkness.
Then is not a preposition
The answer would be B. Answers A, C, and D are fragments of a sentence, lacking a complete idea.
Ex:
A) "because I had not slept for hours" - "because" what? An example of a complete version of this sentence would be "My head hurts because I had not slept for hours."
