For a transverse wave travelling along a straight line, the distance between two peaks (crests) is 5 m, while the distance between one crest and one trough is 1.5 m. The possible wavelengths (in m) of the waves are:
a. 1, 3, 5, .....
b. 11,31,51,…
c. 1, 2, 3, .....
d. 21,41,61,…