Final answer:
The correct answer is C. phosphate groups; hydrophilic.
Step-by-step explanation:
The correct answer is C. phosphate groups; hydrophilic. Hydrophilic interactions refer to interactions between molecules and water. Phosphate groups, which are found in biological molecules like nucleic acids and ATP, have polar characteristics and can form hydrogen bonds with water molecules, making them hydrophilic.
On the other hand, fatty acid groups, which are found in lipids, have nonpolar characteristics and are hydrophobic.