When braking on a slippery surface, you should:
Use both the front and rear brakes.
Use abrupt pressure on the front brake to prevent locking the front tire.
Only use the rear brake.
Use either brake, but use only one brake.
When riding on slippery surfaces, you should use both brakes to slow down. Squeeze the brake lever gradually to avoid locking the front wheel and use gentle pressure on the rear brake.