6. If in space three lines $a$, $b$, and $c$ are pairwise skew lines, then the number of lines that intersect $a$, $b$, and $c$ is
A. 0
B. 1
C. More than 1 but a finite number
D. Infinitely many
Take any point $A$ on line $a$, the plane $\beta$ determined by point $A$ and line $b$ has at most one plane parallel to $c$, otherwise $c / / b$, which is a contradiction. Let the intersection point of plane $\beta$ and line $c$ be $C$, at this time the point $C$ that satisfies $A C / / b$ is also at most one, otherwise $a / / c$. Therefore, let the intersection point of line $A C$ and line $b$ be $B$, thus line $A C$ intersects with $a$, $b$, and $c$. Since there are infinitely many points $A$, there are infinitely many such lines. Therefore, the answer is $D$.