Step-by-step Solution:

Suppose the required point is \(\left(x_{1}, y_{1}\right)\) \[\] \(\frac{d y}{d x}=6-2 x\) \[\] \(6-2 x_{1}=0 \Rightarrow 2 x_{1}=6 \Rightarrow x_{1}=3\) \[\] Point must lie on the curve \[\] \(\Rightarrow y_{1}=6 x_{1}-x_{1}{ }^{2}\) \[\] Putting \(x_{1}=3, y_{1}=18-9=9\), the point is \((3,9)\). \[\] Choice (D)\[\]