Written questions that must be answered, in writing, by the parties to the lawsuit and then signed by the parties under oath are called

A) answers.
B) summons.
C) interrogatories.
D) questionnaires.

Interrogatories

Written questions sent by one party to another in a lawsuit, which must be answered under oath as part of the discovery process.

Under Oath

A legal condition wherein an individual swears to tell the truth or confirms the truthfulness of a statement during legal proceedings.