Two Sinusoidal Waves, Each of Wavelength 5 M and Amplitude

Multiple Choice

Two sinusoidal waves, each of wavelength 5 m and amplitude 10 cm, travel in opposite directions on a 20-m stretched string which is clamped at each end.Excluding the nodes at the ends of the string, how many nodes appear in the resulting standing wave?

A) 3
B) 4
C) 5
D) 7
E) 8