Let's narrow down our choices:
Suspence is something that is included in mystery when you read novel.
Clues are very important when making a piece of Literature that includes mystery. They let us think highly, and gives us predictions.
The NARRATOR does not know everything, he/she could have a tone of voice where he/she is confused on the situation.
A problem in mystery is usually being solved in mystery novels.
The answer to your question is most likely C. I hope I helped!