Final answer:
An attorney is likely to request option A) Exhibits upon submission to a legal portal as these are important pieces of evidence used in a trial or legal proceeding.
Step-by-step explanation:
In legal proceedings, an attorney may request various items upon submission to a portal, but the specific option that fits best from the choices given is A) Exhibits. These are pieces of evidence or documents presented during a trial or deposition to support the case. Options B) Billing details, C) Expedited delivery, and D) Transcriptionist contact are not typically items requested for submission through a legal portal as part of the case-related documents.