Consider different activities related to email. m1: Send an email from a mail client to mail server m2: Download an email from mailbox server to a mail client m3: Checking email in a web browser Which is the applicable level protocol used in each activity
选项：

A:m1:HTTP, m2:SMTP, m3:POP
B:m1:SMTP, m2:FTP, m3:HTTP
C:m1:SMTP, m2:POP, m3:HTTP
D:m1:POP, m2:SMTP, m3:IMAP