If you are driving a taxi and approach a school bus that is stopped with its red lights flashing and stop arm extended, what are you legally required to do?

1. Slow down to 20 km/h and pass carefully
2. Stop at least 20 meters before the bus and remain stopped until the lights stop flashing and the stop arm is retracted
3. Pass the bus on the left side immediately if the road is clear
4. Honk your horn to warn students and proceed past the bus