Water quality is a great concern for sub Sub Saharan Africa's rural population. It is basically a region where water is very scarce and finding the right quality of water for drinking and cooking purposes is very hard for the rural people of this region. I hope the answer helps you.
Answer: C) The climate, fertile soil and large river systems in this region are essential for agriculture and industry.
The answer is when the sun and the moon are at the right angles to the earth
Which make the sun, the earth and the moon formed a 90 degree angle.
during neap tides, the gravitational forces between the 3 counteract one another, creating a weaker tidal forces
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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.