At any time prior to the time set for trial, the defendant may file a written answer admitting or denying all or any of the allegations in the complaint, or pleading new matter in avoidance. No particular form is required, but it is sufficient if in a form to enable a person of common understanding to know the nature of the defense intended. A general denial of all the allegations of the complaint is permissible.
Failure of defendant to file a written answer after being subjected to the jurisdiction of the court over his person constitutes a general denial.