What characterizes a saturated hydrocarbon?

A saturated hydrocarbon is defined by its structure, which is composed entirely of single bonds between carbon atoms and has the maximum number of hydrogen atoms attached to the carbon skeleton. This type of hydrocarbon does not contain any double or triple bonds. The presence of only sigma bonds indicates that all carbon-carbon connections are made through single bonds, fulfilling the criteria for saturation.

The reason this definition is crucial is that saturation impacts the chemical reactivity of hydrocarbons. Saturated hydrocarbons, such as alkanes, tend to be less reactive than their unsaturated counterparts due to the lack of multiple bonds that can participate in chemical reactions.

In contrast, hydrocarbons that contain double bonds (as specified in one of the other choices) are considered unsaturated because they can bond with additional hydrogen atoms, indicating that they do not have the maximum possible number of hydrogen atoms. The other options incorrectly propose that they describe saturated hydrocarbons, as they involve structures with no carbon atoms, or have multiple bonds that would prevent the hydrocarbon from being saturated. Thus, the characteristic that a saturated hydrocarbon contains only sigma bonds and single bonds best captures its nature.