Final answer:
If you accidentally lock the rear brake on a good traction surface, release the brake gradually to regain control of the bike.
Step-by-step explanation:
If you accidentally lock the rear brake on a good traction surface, the force of friction between the brake and the surface will cause the rear wheel to skid. This can result in loss of control and potentially lead to an accident. To avoid this, it is important to release the rear brake gradually to regain traction and regain control of the bike.