A string of length `0.4 m` and mass `10^(-2) kg` is clamped at one end . The tension in the string is `1.6 N`. The identical wave pulses are generated at the free end after regular interval of time , `Delta t` . The minimum value of `Delta t` , so that a constructive interference takes place between successive pulses is
A. 0.05 s
B. 0.10 s
C. 0.20 s
D. 0.40 s