Need on this. i know that it’s not c cause i got it wrong the first time

Lines A, B and D represent constant acceleration that's not zero, because velocity is changing at a constant rate that's not zero.

Line 'c' COULD be a constant acceleration, but you can't tell from the graph.

Part of velocity is the direction of the motion.  If the direction of the motion is changing, then the object is accelerating, but it's really hard to show that on a graph.  

If an object is moving at a constant speed in a circle, like a roulette ball, or a spot on a DVD, or a planet in a circular orbit, or a car going around a curve at 30 mph, then its direction is constantly changing, and that's constant acceleration too.  

the answer is a. hope this .