Which of the following statements is true regarding the chemical properties of alkenes?

Alkenes are characterized by the presence of at least one carbon-carbon double bond (C=C). This double bond consists of one sigma (σ) bond and one pi (π) bond, which plays a crucial role in the reactivity of alkenes. The double bond is susceptible to attack by electrophiles, making alkenes highly reactive compared to alkanes, which only participate in substitution reactions due to their saturation.

The presence of the double bond enables alkenes to undergo addition reactions, where the π bond is broken and new atoms or groups are added to the carbon atoms involved in the double bond. This is a fundamental property of alkenes and underpins many of their chemical reactions, such as hydrogenation, halogenation, and hydration.

In contrast, the other statements do not accurately describe the chemical properties of alkenes. For instance, alkenes are not restricted to substitution reactions (as indicated by the falsehood of option A), and they do not possess high bond enthalpy due to their π bonds; rather, the presence of π bonds typically means lower bond strength compared to σ bonds (which addresses option C). Furthermore, alkenes are not saturated; they are unsaturated hydrocarbons and