Final answer:
The discovery technique where written questions are answered in writing under oath is known as interrogatories.
Step-by-step explanation:
After answering a summons and complaint, Mike received a set of written questions from the plaintiff's attorney, which he was directed to answer in writing under oath. This discovery technique is called interrogatories. Unlike a deposition, which involves oral questioning, interrogatories are strictly a written exchange. They allow the parties in a lawsuit to gather information from each other in preparation for trial. They are different from a request for admission, which asks a party to admit or deny certain facts, and a request for the production of documents, which requires the sharing of tangible evidence.