Question

what is a lipid?
lipids are one of the four major types of large biomolecules found in cells. but unlike nucleic acids, proteins, and carbohydrates, lipids are not defined by distinctive aspects of their structure (such as their component subunits and the bonds that link them into a primary structure). instead, lipids are defined by a physical property: they are not soluble in water. they have few or no polar or charged groups, so interact little or not at all with water. they are hydrophobic - literally water hating.
lipids are hydrophobic because they are dominated by c - c and c - h bonds. recall that because c and h atoms have approximately the same electronegativity, c - c and c - h bonds are nonpolar. as a result, the c and h atoms that dominate lipids are electrically neutral and dont attract the partial positive or negative charges on h and o atoms of water molecules. instead, groups of c - c and c - h bonds will attract each other via hydrophobic interactions, and repel water.
oils are lipids. which statement best explains why oil and water dont mix?
if you try to mix oil and water, the two will separate almost immediately.
the c - c and c - h bonds that dominate oil molecules interact with each other - not water.
oils and waxes are frequently used as water repellents - often as a coating on the surface of furniture or automobiles.
incorrect
this statement is correct but does not address why the phenomenon occurs, which is what the question is asking.

Explanation:

Lipids are defined by their hydrophobicity (not being soluble in water). Oils are lipids. The key is that the non - polar C - C and C - H bonds in oil (lipid) molecules interact with each other (via hydrophobic interactions) rather than with water (which has polar bonds). The first option just describes the separation (a result) but not the reason. The third option is about a use of oils/waxes (a practical application) not the reason for the non - mixing. The second option correctly explains the molecular - level reason (based on bond types and interactions) for why oil (a lipid) and water don't mix.

Answer:

The C - C and C - H bonds that dominate oil molecules interact with each other—not water.