On rubbing an ebonite rod with wool or cat's skin, the electrons from the cat's skin get transferred to the ebonite rod. The cat's skin now has a deficiency of electrons and so is positively-charged. On the other hand, the ebonite rod has an excess of electrons and hence is negatively-charged.
Hence, When an ebonite rod is rubbed with wool, they get oppositely charged due to conduction and the statement is true.