The solution of the partial differential equation d^2 /dt^2 (u(x,t)) - d^2/dx^2 (u(x,t)) = 0 3 u(x,t)_2_u(x,1)=0 satisfying the boundary conditions u(0,1)=0= u(L,t) and initial conditions u(x,0) = sin(xx/L) and __u(x,1)... = sin(27zx/L) is (a) sin(7 x/L)cos(7t/L) + sin(2zx/L)cos(271/L) (b) 2 sin(zx/L) cos(xt/L)-sin(x/L) cos(271/L) (c) sin(x/L) cos(271/L)+sin(2x/L)sin(xt/L) T L (d) sin(xx/L) cos(xt/L) +- -sin(2zx/L)sin(271/L) 2