You are driving on a three-lane highway in Dubai. A car in the leftmost lane, slightly ahead of you, suddenly begins to switch into your lane without indicating. What is the most immediate and appropriate action to take?

1. Honk the horn loudly and accelerate to pass them quickly.
2. Swerve into the rightmost lane to avoid the vehicle.
3. Maintain your lane and brake sharply to let them in.
4. Ease off the accelerator, check your mirrors for space, and be prepared to brake gently.