Answer:
e. None of the above
Explanation:
For me as a Researcher, the reason could be increased Concentration of your DNA sample which you are using as your template. Try to decrease the concentration of DNA (up to 100 ng per reaction is enough and can increase up to 200 ng). so the reason for getting non specific bands is increase concentration of DNA which results in non specific amplification and also degradation of DNA in the reaction which you can see in your gel electrophoresis results.
i always corrected my results using the same technique that is lowering the concentration of DNA between 100 and 200 ng per single reaction of PCR.