The correct answer is C. Deceit.
Duplicity is the act of deceiving someone by concealing the truth or misrepresenting facts. It is often used to gain an advantage or to manipulate someone.
Repetition is the act of saying or doing something again and again. It is often used to emphasize a point or to make something more memorable.
Artlessness is the quality of being simple and natural. It is often used to describe someone who is honest and sincere.
Cleverness is the quality of being intelligent and quick-witted. It is often used to describe someone who is good at solving problems or coming up with new ideas.
In the context of the question, duplicity is the most likely answer because it is the only option that refers to the act of deceiving someone. The other options do not refer to deception.