Final answer:
For a nonpolar stain, a soap or detergent with a strong nonpolar hydrocarbon tail should be used, as it will dissolve the stain, and its polar head will allow the stain to be washed away with water.
Step-by-step explanation:
If a student is dealing with a molecule in a stain that does not have charged regions, meaning it is nonpolar, the recommended soap or solvent should be one that has a nonpolar end capable of dissolving nonpolar substances. This is because soap molecules are amphiphilic, having both a hydrophobic (nonpolar, 'water-fearing') and a hydrophilic (polar, 'water-loving') part. A suitable combination for cleaning such a stain would be a soap with a significant nonpolar hydrocarbon tail that can interact with the nonpolar stain and a polar head that allows the resulting compound to be washed away by water.
The cleansing action of soap is a result of its polar and non-polar structures alongside solubility principles. These molecules form micelles around dirt and oil, encapsulating them in a form that can be easily washed away. Hence, for removing a nonpolar stain, use a soap or detergent with a strong nonpolar functionality, which will dissolve in the stain, while its ionic part will make the soap-stain complex soluble in water, effectively removing the stain.