Lactic acid produced by fermentation causes the sour taste.
I’m pretty sure it’s C if not A
The water repellant properties of waxes is very useful in the leaves of some plants, in the feathers of birds and also in cuticle of insects. Waxes in plant leaves reduce the amount of water that is lost by the leaves. The wax that is present in the birds' feather prevent them from getting wet with water.
The jet stream flows west to east