Answer
Choice D.
Work Step by Step
Points on a horizontally traveling transverse wave oscillate perpendicular to the string. The particle would have a momentary zero velocity only if it were at a crest or trough.
The picture shows that a crest is approaching point B from the left, so a particle in the string there is traveling vertically upward at this moment in time, and will reach that high point after a quarter-period (i.e., T/4) more.
