\textbf{112-} Point $M(x,2)$ lies on the curve $y=2$. It is a variable point. The line segment connecting point $M$ to the origin, makes an angle $\alpha$ with the positive $x$-axis. The rate of change of $\alpha(x)$ with respect to $x$, at the moment $x=4$, is which of the following?
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(1) $-0/2$ \hfill (2) $-0/1$ \hfill (3) $0/05$ \hfill (4) $0/15$
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