10. For any four rational numbers $a, b, c, d$, define a new operation: $\left|\begin{array}{ll}a & b \\ c & d\end{array}\right|=a d-b c$. Given $\left|\begin{array}{cc}2 x & -4 \\ x & 1\end{array}\right|=18$, then $x=(\quad$.
(A) -1
(B) 2
(C) 3
(D) 4
Reference answer: C
