Draw displacement time graph from velocity time graph

[jigoku_snow]

hey there, I'm a little confuse on how to draw a s-t graph from a v-t graph :( based on the graph attached, the displacement of C is lesser than D, but why the s-t graph is not like in a 'bell' shape ( curve down from D to C) ? instead it went up? if the question were to ask for a distance-time graph, will it be in the same shape?

 

[bp_psy]

The velocity is always positive in that graph so of course the displacement will allways increase.