(a) and (b) See if the velocity is positive or negative at the point. If it is positive the particle is traveling in the positive direction on the axis and if it is negative the particle is moving in the negative direction.

(c) The direction of motion reverses at points where the velocity is zero. This is not always true but for this graph the sign of the velocity is different on the two sides of a zero.

(d) The acceleration is the slope of the velocity versus time graph.

[(a) positive direction; (b) negative direction; (c) 3 and 5; (d) 2 and 6 tie, then 3 and 5 tie, then 1 and 4 tie (zero)]