In the Cartesian coordinate system, the equation
$$
x^{2}+2 x \sin x y+1=0
$$

represents the figure ( ).
(A) a straight line
(B) a parabola
(C) a point
(D) none of the above
-,1. D.
It is known that, $x=-1, \sin x y=1$, or $x=1, \sin x y=-1$.

Therefore, the graph represented by this equation consists of the point sequences $\left(-1,2 k \pi-\frac{\pi}{2}\right)$ $(k \in \mathbf{Z})$ and the point sequences $\left(1,2 k \pi-\frac{\pi}{2}\right)(k \in \mathbf{Z})$.