What should you NOT do in the event of hydraulic brake failure?

Answer: A — Shift up

In the context of hydraulic brake failure, shifting up is not an advisable action. When hydraulic brakes fail, the immediate focus should be on controlling the vehicle safely. Shifting up into a higher gear can make it more difficult to slow down the vehicle, as you would be reducing engine braking and potentially increasing speed. Instead, the correct response involves utilizing the emergency brake, pressing the brake pedal firmly, and checking for leaks—actions that help to manage the situation effectively and bring the vehicle to a stop safely. Using the emergency brake engages a different braking mechanism that can often help in slowing the vehicle down when the hydraulic brakes are compromised. Checking for leaks can assist in identifying the problem and potentially restoring some braking function. Pressing the brake pedal firmly may also provide some residual braking power, depending on the vehicle's brake system design. Shifting up, however, does not offer any benefit in this scenario and could worsen control of the vehicle.