
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
If the function $f(x) = x^3 - 12x$ is not a monotonic function in the interval $(k-1, k+1)$, then the range of real numbers for $k$ is (　　)

A) $k \leq -3$ or $-1 \leq k \leq 1$ or $k \geq 3$

B) $-3 < k < -1$ or $1 < k < 3$

C) $-2 < k < 2$

D) There is no such real number

Present the answer in LaTex format: \boxed{Your answer}
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