Which of the Following Statements About the Reaction Shown Here

Which of the following statements about the reaction shown here is true?

I. The alkene is a Brønsted base.
II. The alkene is a Brønsted acid.
III. The rate-limiting step is carbocation formation.
IV. The rate-limiting step is nucleophilic attack by chloride ion on a carbocation.

A) I, III
B) I, IV
C) II, III
D) II, IV
E) I only