Hydrocarbons are generally insoluble in water primarily because the majority of their bonds are nonpolar covalent carbon-to-hydrogen linkages.
Water is a polar solvent, which means it has a positive and a negative end due to the unequal sharing of electrons between oxygen and hydrogen atoms. Polar solvents tend to dissolve substances that are also polar (like salt or sugar) due to interactions such as hydrogen bonding.
On the other hand, hydrocarbons consist largely of nonpolar bonds, and because of this nonpolarity, they do not interact favorably with the polar molecules of water. This nonpolarity leads to a lack of solubility, as "like dissolves like" in chemistry. Therefore, the correct reason for hydrocarbon insolubility in water is: The majority of their bonds are nonpolar covalent carbon-to-hydrogen linkages.