$4 \cdot 35$ The set of all real solutions to the inequality $| x-1|+| x+2 |<5$ is
(A) $\{x:-3<x<2\}$.
(B) $\{x:-1<x<2\}$.
(C) $\{x:-2<x<1\}$.
(D) $\left\{x:-\frac{3}{2}<x<\frac{7}{2}\right\}$.
(E) $\varnothing$ (empty set).
(24th American High School Mathematics Examination, 1973)