5.5 In the same coordinate system, the graphs of the functions $y=k x+b$ and $y=\frac{k b}{x}(k \neq 0, b$ $\neq 0)$ can only be
(A)
(B)
(C)
(D)
(Mathematics League of Junior High Schools in Guangzhou, Wuhan, Fuzhou, and other five cities, 1989)
[Solution] If $k b>0$, then the graph of $y=\frac{k b}{x}$ is like $(A),(B)$, while $y=k x+b$ is like $(B),(C),(D)$. Therefore, (B) satisfies both equations.

If $k b<0, y=\frac{k b}{x}$ is like $(C),(D)$, and $y=k x+b$ is like $(A)$, which cannot satisfy both equations simultaneously.
Hence, the answer is $(B)$.