The correct answer is: Version of POP.
POP3 stands for Post Office Protocol version 3. It is a standard Internet protocol for accessing email from a remote server. POP3 is the third version of the POP protocol, and it is the most widely used version.
The numeric value ‘3’ in POP3 represents the version of the protocol. The first version of POP was released in 1984, and the second version was
released in 1988. POP3 was released in 1995, and it is the most widely used version of the protocol.The other options are incorrect. Option A is incorrect because the numeric value ‘3’ does not represent the number of codes in POP. Option B is incorrect because the numeric value ‘3’ does not represent the number of characters in POP. Option C is incorrect because the numeric value ‘3’ does not represent the header size of POP.