38. Why do fragments of DNA separate when using gel electrophoresis? a. There is a magnetic field causing the DNA fragments to move b. A diffusion gradient acts as a sieving medium through which DNA fragments are moved C. Charged DNA molecules are repulsed by the electrically charged gel ions d. It is a sieving medium through which DNA molecules are moved by electrical forces e. There is a movement through a sieving medium by positively charged DNA molecules attracted by a negative pole