A.FTP B.HTTP C.SMTP D.TelNet
A.Insert Into users(id,user_name) Values(100, "luhong") B.Insert Into users(real_name,tel) Values("盧紅","6545632") C.Insert Into users(user_name,Email) Values("luhong", "") D.Insert Into users(user_name,Email) Values("luhong", NULL)