cesium sulfate solubility decreases with decrease in temperature (answer C) change in temperature led to the change in kinetic energy.The lower kinetic energy the lower the solubility.Decrease in temperature led to lower kinetic energy hence lowering the solubility.
Answer : The Product are the new substances that are created following a chemical reactions.
Explanation :
Chemical reaction : A chemical reaction occur when two or more reactants react to form a new substance.
Reactant : A substance that is involved in a chemical reaction.
Product : A new substance that is formed in a chemical reaction.
For example : 
In this, A and B are the reactants and AB is the product.
Therefore, the answer is Product.
My guess would be; soil needs water to survive and sand does not.
The answer is d you are welcome