Manuel and Sandy were partners. Sandy held the accelerometer in her hands while Manuel watched the water line. Throughout Sandy's walk, the water line remained level. What does that tell the students about Sandy's motion? A) Sandy's velocity changed when she slowed down or sped up.
B) Sandy's speed might have changed but her direction did not.
C) Sandy must not have been moving if the water line remained level.
D) Sandy's velocity is constant; her speed and direction did not change.