Speaking from experience, I used to often line up in position B in order to allow me to waive right turners through. However, I now line up at C or between C and B. The reason: I was in position B, waving right turners through, assuming only right turners would slip by. However, the light changed from red to green, the straight though traffic took my waive to mean I was waiving them through. After 10 or so cars slid by on my right, picking up speed with each car, with me sitting there like a sitting duck between lines of moving traffic, I made the decision that B is about the worst place I could B. If its not too busy, B may be fine but with heavy traffic, I will take C or between B and C.