Which of the following is a form of discovery in civil cases?

Interrogatories are a formal method of discovery in civil cases, involving written questions that one party sends to another party. These questions must be answered in writing and under oath, allowing each side to gather information crucial for the litigation process. This method is particularly useful for clarifying facts, obtaining admissions, and understanding the opposing party's arguments and positions before trial.

In contrast, while physical evidence collection, witness interviews, and cross-examinations are all relevant to the overall process of preparing for and conducting a civil case, they do not fit the technical definition of discovery in the same way. Physical evidence collection pertains to gathering tangible items or documents for evidence, witness interviews may occur informally or as part of depositions rather than as formal discovery, and cross-examinations are a part of the trial process where witnesses are questioned in front of a judge and jury, rather than a pre-trial discovery method.