In gel electrophoresis dna molecules migrate from to ends of the gel.

a, acidic basic
b, negative positive
c, basic acidic
d, long short
e, positive negative

b, negative ... positive

Explanation:

Gel electrophoresis is  a method used in molecular biology for DNA analysis. This method includes the separation of DNA fragments through the gel according to their size or shape under the influence of aplid electric current. Since the fragments of DNA are negatively charged, they will move from negative to positive end.

Small fragments will move faster than larger ones.

One of the major source of error is contamination of the DNA sample. This refers to the presence of foreign DNA in the sample of interest. As a consequence, the gel will have more bands.

Another errors might appear as a result of wrong concentration of the gel, wrong buffer pH, high/low concentration of dye etc.