Final answer:
The correct answer is a) Hydrocarbon; Hydroxyl, as lipids have a hydrophobic hydrocarbon portion and may have polar groups like hydroxyl that affect their solubility.
Step-by-step explanation:
Lipid molecules contain a large hydrocarbon (HC) portion and many have hydroxyl groups, which account for their solubility behavior.
The correct answer to the question is: a) Hydrocarbon; Hydroxyl. Lipids have a long alkyl group (hydrocarbon) that provides them with a hydrophobic or lipophilic character, making them insoluble or poorly soluble in water. However, some lipids also have polar groups such as hydroxyl groups that can interact with water, which influences their solubility behavior to some extent.