What is indicated by a subpoena ad testificandum?

A subpoena ad testificandum specifically refers to a legal order that requires an individual to appear in court and testify as a witness. This type of subpoena is focused on compelling the presence of a person to provide oral testimony related to a case. In this context, option C is correct because it clearly indicates the obligation to come prepared to give testimony, which is the essence of what a subpoena ad testificandum entails.

The other choices do not accurately reflect the nature of a subpoena ad testificandum. While presenting evidence in court is a broader task that may be associated with witness testimony, it does not convey the specific obligation that comes with this type of subpoena. Supplying written documents is related to a different type of subpoena, known as a subpoena duces tecum, which orders the production of documents or records rather than testimony. A summary judgment, on the other hand, is a legal ruling by a judge on a case based on the presented evidence, and it doesn't pertain to an individual’s obligation to testify. Thus, option C succinctly captures the meaning and legal requirement associated with a subpoena ad testificandum.