I'll answer C, strapped to my back. Well, I don't know about ideal, but with the various bags/panniers I have now, it's a lot faster and easier to use my backpack. Don't get me wrong, I have front and rear racks and wald folding baskets for groceries, but on the commute, it just works better for me to be wearing the weight rather than have it strapped to my bike.


Tip: sternum and hip straps are key.