20. If the graph of the function $y=k x^{2 k^{2}+k-2}$ is a hyperbola, and it is in the second and fourth quadrants, then $k=(\quad)$.
(A) $\frac{1}{2}$
(B) -1
(C) $-\frac{3}{2}$
(D) 1
20. B.

From $\left\{\begin{array}{l}k<0, \\ 2 k^{2}+k-2=-1,\end{array}\right.$ we solve to get $k=-1$.