unsure how to solve this

How many of the following functions satisfying the wave equation utt (I, t) = d'un,(1, t), where a is a constant. . u(x, t) = sin(kr) sin(akt) u(x, t) = t/(at2 _ 12) . u(x, t) = (x - at)6 + (x + at)6 . u(x, t) = sin(x -at) + In(x - at)