C. Environmental Service Systems
Answer:
Short for Post Office Protocol, POP or POP mail is one of the most commonly used protocols used to receive e-mail on many e-mail clients. There are two different versions of POP: POP2 and POP3. POP2was an early standard of POP that was only capable of receiving e-mail and required SMTP to send e-mail. POP3 is the latest standard and can send and receive e-mail only using POP, but can also be used to receive e-mail and then use SMTP to send e-mail.
A Would be the answer, Sir.!
the role of an os or operating system is the program that executes everything and makes the computer usable hope this helps
