Montion graphs

The first three answers of the middle row are wrong.
As velocity keeps increasing, the displacement should be curve.
When velocity increases, the curve tends to vertical. When velocity decreases, the curve tends to horizontal.
d part. The displacement decreases in constant slope. The velocity is constant and negative. (coz s/t = v, the slope(s2-s1/t2-t1) is constant therefore v too). No change in velocity(horizontal straight line on the negative zone) means acceleration is zero.