The diagram presents a velocity-time graph for a vehicle. At time $= 0$, the vehicle, travelling at $4.0\,\text{m s}^{-1}$, starts to accelerate. What is the vehicle’s acceleration at time $= 3.0\,\text{s}$?
- A$0.67\,\text{m s}^{-2}$
- B$1.0\,\text{m s}^{-2}$
- C$1.3\,\text{m s}^{-2}$
- D$2.0\,\text{m s}^{-2}$