Answer:
Erosion is the washing away of the uppermost part of the earth crust. Once erosion starts it only gets worse because, erosion wash away further soil, causing the eroding channel to futher expand, increasing the erosion.
Lack of vegetative cover allows erosion which washes away soil nutrients, further worsening the soil against soil vegetative cover.
Answer:

Recommended daily Amount (RDA) of magnesium is 410,000 μg/day.
Explanation:
There are 1000μg in 1 mg and 1000 mg in 1g
1 mg=1000μg
The Recommended daily Amount (RDA) is 410 mg/day of magnesium. Converting 410 mg/day into μg/day

It will become 410,000 μg/day
So Recommended daily Amount (RDA) of magnesium is 410,000 μg/day.
Answer: The missing coefficient is 2.
Explanation:
According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products has to be equal to the mass of reactants. The number of atoms of each element has to be same on reactant and product side. Thus chemical equations are balanced.

As in the products, there are 2 atoms of sodium, thus there will be 2 atoms of of sodium in the reactant as well. This will balance the number of hydrogen and oxygen atoms as well.
Thus the missing coefficient is 2.
The property to be used is sieving. you get a bowl and a sieve when you pour the sand and salt,the salt being the small particle sieve to the bowl while the sand remain on the sieve as residue