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Given the function, what is the best statement for the equation $y={ x }^{ 3 }- { x }^{ 2 }-2x$?

The Mean Value Theorem guarantees a maximum on the interval $[-1,2]$.

The Mean Value Theorem guarantees at least one horizontal tangent on the interval $[-1,2]$.

The Mean Value Theorem guarantees exactly one horizontal tangent on the interval $[-1,2]$.

The Mean Value Theorem guarantees exactly two horizontal tangents on the interval $[-1,2]$.