After stopping on an uphill grade, when rejoining traffic you should:

When rejoining traffic after stopping on an uphill grade, it is essential to ensure stability and control of the vehicle. Utilizing the parking brakes is a recommended method to prevent the vehicle from rolling backward as you prepare to accelerate. By holding the vehicle using the parking brakes until the clutch engages, you can smoothly transition back into a forward motion without the risk of losing control due to gravity. This technique not only enhances safety but also provides the driver with the necessary confidence to merge into traffic effectively.

The other approaches, such as keeping the clutch slipping while slowly accelerating, could lead to unnecessary wear on the clutch and may result in a lack of power to move forward. Allowing the vehicle to roll backward before engaging the clutch defies the need to maintain control and poses a risk to the driver and surrounding vehicles. Disengaging the clutch while revving the engine does not provide the proper engagement needed to effectively move the vehicle forward on an incline and could lead to potential stalling. Overall, using the parking brakes is the safest and most effective method in this scenario.