When approaching a highway tunnel entrance during bright daytime conditions, what visual phenomenon occurs and how should the bus driver respond?

1. The 'black hole effect' (黑洞效应) causes temporary visual impairment; the driver must reduce speed and turn on low-beam headlights before entering the tunnel
2. The 'white hole effect' occurs; the driver must put on dark sunglasses and accelerate into the tunnel
3. Tunnels have no lighting changes; drivers should maintain maximum expressway cruising speed
4. The driver should turn on high beams and hazard flashers while honking continuously