A PCR amplification was done on a positive control containing the template DNA, a negative control ...

A PCR amplification was done on a positive control containing the template DNA, a negative
  control without the template DNA and two samples. Oligonucleotide primers of 21 base pairs
  were used, and the expected amplicon product is about 160 base pairs
 
  Observe the agarose gel
  electrophoresis done on the amplicons, and give the most appropriate interpretations.
  A) The assay must be repeated because the negative control is not negative.
  B) The assay must be repeated because the amplicon is not the right size.
  C) The assay must be repeated because there is evidence of primer dimer formation.
  D) Sample 1 is positive for the template DNA, and sample 2 is negative for the template
  DNA.
  E) The assay must be repeated because the positive control has more than one amplicon.