The answer is (4) synthesis. Synthesis reaction means that two or more reactants combine directly to one production. Substitution or single replacement means that one element of a compound is replaced by another element. Double replacement means that two ionic reactants exchange ions to form two new productions.
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The answer is D, Salinity.
Salinity is the concentration of salt in water. Ocean water often has high salinity and this can contribute to things like upwelling and water density- but these all start from salinity.
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When sodium amide i.e.
reacts with water i.e.
results in the formation of sodium hydroxide i.e.
and ammonia
.
The chemical reaction is given by:

Now, when ammonia i.e.
reacts with water results in the formation of ammonium hydroxide i.e. 
The chemical reaction is given by:

Thus, the products of the above reactions are ammonia and ammonium hydroxide (without sodium ion).
The structures of the products are shown in figure (1): ammonium hydroxide and figure (2) ammonia.
B. The mouse is hungry , because you dont really know that only the mouse does