There is no 'wrong side of the road' here . (Why posters keep saying this is a bit worrying.)
You can use both lanes of a road.
Unless there are double white lines, you can move from the left to the right, if your way is clear.
The 'wrong side of the road' is only relevant is a car overtakes and pulls into oncoming traffic and causes an accident.
It is absolutely crystal clear that CAR C is in the wrong.
It's a classic driving mistake.
Pulling out at a junction when being unsighted.
The speed of Car A is irrelevant. (Except as a speeding offence which is separate to the collision.)
The position of Car A is irrelevant.
The decision of Car C to emerge from a side road, when they were not 100% sure of what was coming from their right, is why there was a collision.
I am shocked at so many responses here and hope, to God, that if some of you are driving, you rethink your driving skills.