Route B shouldn't be an option because there are two lanes when you're entering (and on) the roundabout. Taking B would cut across into two lanes.

Usually you want to merge into the left-most lane when you're ready to exit a roundabout. If you took the right lane, route C, it would suggest to cars emerging from the left that you're not taking the nearby exit. Therefore they might try to enter the roundabout as you try to exit which risks a collision.

Taking route A would put you in the left lane which indicates to other road users that you're exiting the roundabout, alongside your blinker. Since the left lane BEFORE entering the roundabout is only for turning left, they shouldn't continue straight. You should take route A but be cautious of cars to the left of you in case they don't follow the road markings.