Answer:
Use a higher % agarose gel.
Explanation:
Agarose gels have a porous matrix. The higher the concentration of agarose, the smaller the pores, so larger DNA molecules will have more difficulty moving through the gel and they will run slower than small DNA molecules.
The higher % agarose gel has thus a better resolving power (the measurable interval between two entities -the DNA bands- is smaller). For that reason, a 2% agarose gel will allow you to differentiate better between two bands of close molecular weight, if you let the DNA fragments run long enough.