(a) When any ground for objection to a complaint, cross-complaint, or answer appears on the face thereof, or from any matter of which the court is required to or may take judicial notice, the objection on that ground may be taken by a demurrer to the pleading.
(b) When any ground for objection to a complaint or cross-complaint does not appear on the face of the pleading, the objection may be taken by answer.
(c) A party objecting to a complaint or cross-complaint may demur and answer at the same time.