Answer:
By eating things with protein in it. Sorry if this sounds too simple, but that's all it is.
The correct answer is "intake and excretion are equal." Normally, there should be equilibrium between the intake of sodium and the excreted sodium. There are regulatory mechanisms in the body that regulate the excretion of sodium in order to match it with the intake. This is to prevent hyponatremia and hypernatremia.
I believe that the best answer for this question is "gene mutations." Gene mutations can either take place through nucleotide substitutions, which occur when the the sequence of nucleotides are altered. Frameshift mutations can also occur. They involve the insertion or deletion of a DNA molecule's bases. Hope this helps.