多项选择题 By default, which of the following ports would a network need to have opened to allow for thetransmission of incoming and outgoing email?（） (Select TWO).

单项选择题 A technician receives an urgent call that the switch in accounting is down. Which of the followingshould the technician do FIRST to troubleshoot this issue?（）

单项选择题 Which of the following is a performance optimization technology?（）