Which of the following is an example of a hydrophobic molecule?

Hydrophobic molecules are characterized by their inability to mix or interact with water. They do not form hydrogen bonds with water molecules and are typically nonpolar. In this context, oil is an excellent example of a hydrophobic molecule. Its molecular structure is predominantly nonpolar, preventing it from interacting well with polar substances like water.

The other options presented are all hydrophilic to varying degrees. Glucose, for instance, is a polar molecule with multiple hydroxyl (–OH) groups that facilitate interactions with water. Salt, or sodium chloride, dissociates in water to form ions, making it highly soluble and therefore hydrophilic. Ammonia, while not as polar as water, can still engage in hydrogen bonding, allowing it to dissolve to some extent in water. Therefore, oil stands out as the correct example of a hydrophobic molecule due to its nonpolar nature.