Final answer:
Nonpolar groups are capable of only hydrophobic interactions, which occur between molecules that are not attracted to water. Fatty acid groups are an example of hydrophobic groups that tend to aggregate away from water, which is essential in processes like protein folding.
Step-by-step explanation:
The group capable of only hydrophobic interactions is c) Nonpolar groups. Hydrophobic interactions are a type of van der Waals force that occur between nonpolar molecules or groups, causing them to aggregate and minimize their contact with water. This is because hydrophobic molecules are nonpolar and do not mix with water, which is polar. For instance, fatty acid groups are hydrophobic, while phosphate groups are hydrophilic and capable of hydrogen bonding. Hydrophobic interaction is critical in protein folding, where nonpolar amino acid side chains tend towards the interior, away from water.
Alkyl groups are another example of hydrophobic groups, which repel water molecules due to their nonpolar nature. The hydrophobicity of substances like alcohols can vary based on the length of their alkyl chain, with larger chains generally increasing hydrophobic character and decreasing solubility in water.