Which graph corresponds to an object moving with a constant negative acceleration and a positive velocity?

a = -Rdv/dt = -R∫dv = R∫dt
V = -pt + c → straight line
Now, dv/dt = -R.V
dv/dn = -R → ∫vdv = -∫p dn → v²/2 = -Rx + c → v² = -Rxn + 2c - Parabola