Answer:
positive at (a) t = 1s
zero at (b) t = 2s
negative at (c) t = 3s
Step-by-step explanation:
the motion of the object is positive at 1s because the line is being curves upwards. the motion of the object is zero at 2s because upwards motion has peaked, and downwards motion has not started yet. the motion of the object is negative at 3s because the line is curving downwards.