Final answer:
During gel electrophoresis, DNA with 3,500 base pairs will travel further than DNA with 6,000 base pairs because it is smaller and experiences less friction. option b.
Step-by-step explanation:
The DNA that will travel the farthest during gel electrophoresis is the DNA with the smaller number of base pairs. This is because DNA has a negative charge and will be attracted towards the positive electrode during gel electrophoresis. Smaller DNA molecules, such as a DNA with 3,500 base pairs, will be able to move faster and travel further through the gel compared to larger DNA molecules, like a DNA with 6,000 base pairs, due to experiencing less friction and having a smaller physical size. Therefore, a DNA molecule with 3,500 base pairs will travel farther than a DNA molecule with 6,000 base pairs in gel electrophoresis.