The Displacement of a Vibrating String Versus Position Along the String

Multiple Choice

The displacement of a vibrating string versus position along the string is shown in the figure. The periodic waves have a speed of 10.0 cm/s. A and B are two points on the string.
-What is the amplitude of the wave?

A) 2 mm
B) 4 mm
C) 8 mm
D) 12 mm
E) 16 mm