It doesn't sound important
The answer is d I took the test
Wind erosion is the main cause. And since it is the desert that wind can pick up tiny sand rock particles that slowly grind against the rock. Over time the erosion will give a jagged rock the smooth features as if it had been submerged in a river for the roughly same period of time.
Coal workers' pneumoconiosis (CWP), commonly known as "black lung disease," occurs when coal dust is inhaled. Over time, continued exposure to the coal dust causes scarring in the lungs, impairing your ability to breathe.
