(4) $l$ and $l^{\prime}$ are mutually perpendicular skew lines, $l$ is parallel to plane $\pi$, and $l^{\prime}$ lies in plane $\pi$. The locus of points in plane $\pi$ that are equidistant from $l$ and $l^{\prime}$ is ( ).
(A) Line
(B) Ellipse
(C) Parabola
(D) Hyperbola