5.2 Let $b>a$, plot the graphs of the linear functions $y=b x+a$ and $y=a x+b$ in a Cartesian coordinate system, then there is a set of values for $a$ and $b$ such that one of the following 4 figures is correct.
(A)
(B)
(C)
(D)
(Chinese Junior High School Mathematics League, 1999)
[Solution] The intersection point $(x, y)$ of the two lines is the solution to the system of equations $\left\{\begin{array}{l}y=b x+a, \\ y=a x+b\end{array}\right.$, which is $(1, a+b)$.
In (A), the x-coordinate of the intersection point is negative, so (A) is incorrect.
In (C), the x-coordinate of the intersection point is $2 \neq 1$, so (C) is incorrect.
In (D), the y-coordinate of the intersection point is a number greater than $a$ and less than $b$, not $a+b$, so (D) is incorrect. Since only one of the four options is correct, (B) is the correct choice.
Therefore, the answer is (B).