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 frequency of the wave?

A) 0.60 Hz
B) 0.90 Hz
C) 1.1 Hz
D) 1.3 Hz
E) 1.7 Hz