In this task, you will be presented with a multiple-choice question in Persian, and you should answer the question based on your knowledge. Classify the answers based on options.
Q: عبارت DOS برگرفته از حروف اول کدامیک از عبارات زیر میباشد؟ <sep> (A) Disc Operating Single (B) Disk Operating System (C) Disk Opening Source (D) Disk Open System
A: 
B