1991 AHSME Problems/Problem 18

If $S$ is the set of points $z$ in the complex plane such that $(3+4i)z$ is a real number, then $S$ is a

(A) right triangle (B) circle (C) hyperbola (D) line (E) parabola The problems on this page are copyrighted by the Mathematical Association of America's American Mathematics Competitions. AMC logo.png