EjsS Position vs Time Graph Problem 2.1

EjsS Position vs Time Graph Problem 2.1
taken from http://www.compadre.org/osp/items/detail.cfm?ID=13049
authors: Andreu Glasmann, Wolfgang Christian, and Mario Belloni, some edits(refer to below) by lookang

The EjsS One-Dimensional Kinematics Problem Package contains JavaScript adaptations of Physlet problems from Physlet Physics Chapter 2. The problems in this package are interactive versions of the kind of exercises typically assigned for homework.
The EjsS One-Dimensional Kinematics Problem Package was developed using the Easy Java/JavaScript Simulations (EjsS) version 5. Although EjsS is a Java program, it can create stand alone JavaScript programs that run in almost any PC or tablet.
The equation that model the motion of the car is:

δxδt=v

δvδt=a

https://dl.dropboxusercontent.com/u/44365627/lookangEJSworkspace/export/ejss_model_Problem2_1wee/Problem2_1wee_Simulation.html
source: https://dl.dropboxusercontent.com/u/44365627/lookangEJSworkspace/export/ejss_src_Problem2_1wee.zip
reference: http://webphysics.davidson.edu/physlet_resources/physlet_physics/contents/mechanics/one_d_kinematics/prob2_1.html
author: Andreu Glasmann, Wolfgang Christian, and Mario Belloni, lookang (this version)

changes made by lookang include:

fix bug of graph C to truly coincident with the displacement starting with -1.7
added answer?
add seconds text
add world view text with circles of equal time interval for easier associated sense of the change in displacement at equal time intervals
made it easier to identify the correct answer is "C"
enjoy!