Defendant's 3 Choices after Receiving the Complaint

What options are available to the defendant upon receipt of the complaint?

[1] Filing of a motion for bill of particulars. He may ask the plaintiff to clarify ambiguous parts of the complaint.
[2] Filing of a motion to dismiss. He may ask the court to throw the complaint out of court if any of the grounds under Rule 16 exists.
[3] Filing of an answer to the complaint. He may answer the complaint and incorporate his defenses and objections. He may also include a counterclaim in his answer.