Question 1199100
The initial displacement at t = 0 is non-zero, thus the model must 
use a cosine function. If the frequency is 4/3 cycles per sec, and 1 cycle
is 2*pi, the angular frequency is 8*pi/3. The general form of the function is:
d(t) = A*cos(w*t) there A = the amplitude and w = the angular frequency.
For this case A = 5 and w = 8*pi/3, so the answer is A).
The graph is below:
*[illustration SHM.png]