All of the following would be considered symptoms (rather than signs) except:
a. cough
b. sensitivity to light
c. hot flashes
d. acidosis

C. Acidosis

Explanation:

A symptom is a version of the manifestation of a sickness given by the patient. It can vary from patient to patient and is subjective. The signs come from the examination of the patient and are objective and measurable throughout a system of units ( C, mm Hg, other). Acidosis is a sign because it requires laboratory tests.

Dominance involves one allele masking another at the same locus whereas epistasis involves one locus masking a different locus.

Explanation:

Epistasis is a type of gene interaction in which one gene masks or modifies the expression of another gene at a distinct locus.

Dominance refers to the gene interaction in which one allele of a given gene masks the expression of another alllele of same gene.

The comparison of dominance and epistasis give the following  information:

Dominance  involves  allelic suppression while epistasis involves non-allelic suppression.Dominance involves a single pair of alleles while epistasis involves two pairs of allele.In dominance, the expression of recessive allele is suppressed while in epistasis, either recessive or dominant  non allele is suppressed.The effect of dominance is due to the dominant allele while epistasis may be due to dominant or recessive allele.