A yellow ABS malfunction lamp stays on after the bulb check while the bus is underway. What should the driver understand?

1. The bus still has regular brakes, but ABS control may be lost at one or more wheels and the system should be serviced
2. The bus has no brakes at all and must be abandoned immediately
3. ABS will shorten every stop, so no action is needed
4. The driver should pump the brakes to reset ABS