\textbf{164.} The position–time graph of a moving object with constant acceleration is shown below. The slope at moment $t = 8$ s is equal to $t = 8$ s. How much is the slope at moment $t = 2$ s?
\textit{[Figure: position-time graph $x$ vs $t(\text{s})$, curved line passing through points near $t = 4$ and $t = 10$]}
\begin{itemize}
\item[(1)] 2
\item[(2)] 3
\item[(3)] 4
\item[(4)] 5
\end{itemize}