Which car is turning left correctly here?

You should try to cross the smallest number of lanes possible when you turn left. That is, turn from the left lane into the left lane. Don't change lanes mid-turn and don't cross any more lanes than you need to. Here Car A has incorrectly turned into the right lane. [Left Turns, How to Drive Safely, Chapter 6 - Driving Safely and Studying for Your Permit, Vermont Driver's Manual]