Question

when should cyclists brake by using mainly the rear brake?
when going downhill
when almost stopped
when going uphill
when just starting to brake

Explanation:

When a cyclist is almost stopped, using the rear - brake is more appropriate. Using the rear - brake mainly when going downhill can cause skidding, using it when going uphill is not the main time for rear - brake use, and when just starting to brake, a combination of front and rear brakes is usually better.

Answer:

when almost stopped