单项选择题 An administrator attempts to open a web page and sees the following error: Error 404: Page not found. The administrator then uses the ping command and finds that the default gateway cannot be pinged. At which of the following layers does the problem MOST likely reside?（）

单项选择题 The technician notices that one of the wires in a CAT5 cable is cut in half. Which of the followingconnectivity issues did the technician discover?（）

单项选择题 Which of the following cable types is intended to be used on short distances and is immune to anytype of interference?（）