In the Three Previous Problems, the Solution For $u ( x , t )$

In the three previous problems, the solution for $u ( x , t )$ is

A) $u = \sin ( \pi ) u ( t - x / a )$
B) $u = \sin ( \pi ( t - x / a ) ) u ( t - x / a )$
C) $u = \sin ( \pi x ) \cosh ( \pi t )$
D) $u = \cos ( \pi x ) \sinh ( \pi t )$
E) $u = \cos ( \pi ( t - x / a ) ) u ( t - x / a )$