[Evaldas]

Which of these substances butane and butene will react?
A Br₂(aq)
B KMnO₄(aq)
C H₂(g)
D Cl₂(g)

For some reason the correct answer is supposed to be D, but I don't understand why. Only butene would react with hydrogen gas, and only butene would oxidize with KMnO₄, however both alkanes and alkenes react with halogens, then why is it chlorine instead of bromine?

[Schrödinger]

Option A says Bromine is in the aqueous form. Only gaseous halogens react with alkanes  is the presence of a free radical initiator. Aqueous Bromine reacts with alkenes via a cyclic Bromonium intermediate