The rope shown at an instant is carrying a wave travelling towards right, created by a source vibrating at a frequency n . Consider the following statements
I. The speed of the wave is `4n xx ab`
II. The medium at a will be in the same phase as d after `(4)/(3n)s`
III. The phase difference between b and e is `(3pi)/(2)`
Which of these statements are correct
A. I, II and III
B. II only
C. I and III
D. III only
