Final answer:
The safest action to avoid a collision with a cyclist is to slow down and allow the cyclist to move ahead. Honking can help alert the cyclist, but it does not replace the need to reduce speed. Abrupt lane changes should be avoided unless safe to do so.
Step-by-step explanation:
As the driver of vehicle A, about to collide with a cyclist who pulled out ahead, the safest and most appropriate action to take would be to slow down and allow the cyclist to move ahead(C). Accelerating and overtaking quickly could be dangerous and may not be feasible depending on traffic conditions. Honking the horn can serve as an alert but should not replace the need to slow down. Abruptly changing lanes can create a hazard for other vehicles and is not advised unless it can be done safely. In all cases, avoiding a collision with a cyclist is paramount, as cyclists are considered vulnerable road users.