Which hydrocarbon will most likely undergo an addition reaction with br2?

Complete question along with options is attached below,

            Option-B (Ethene) is the correct answer.

Explanation:
                   In given options except option-B (an alkene) all options are example of alkanes.
                    
Reason for reactivity of Alkene:
                                                      Alkenes are more reactive than alkanes because it consists of a pi bond. Thus, the electron density in this pi bond lies below or above the bond axis, hence making it more exposed and accessible for incoming electrophile.
                                      Secondly, the pi bond is weaker than sigma bond and can easily break down. This weakness originates due to less effective overlap of the orbitals forming pi bond as compared to the overlap resulting in the formation of sigma bond.
                                      Therefore, alkenes can add Br₂ through a electrophillic addition reaction, while alkanes fail to show such reaction.

True, the standard unit for volume is liters which can be represented by either a lower case "l" or a capital "l"