user
I killed one fourth of mankind.  Who am I?
A: assassination
B: harm
C: cain who killed abel
D: stiletto
E: conquer enemy
assistant
<|begin_of_thought|>

Deep Thought is thinking for 7.5 million years.

<|end_of_thought|>

<|begin_of_solution|>

C

<|end_of_solution|>