Study the exhibit shown below carefully. A Cisco Aironet Wireless LAN Client Adapter has been  installed and configured through the ADU on the PC. The Aironet System Tray Utility （ASTU） has  been enabled during the installation and the icon appears in the system tray area in the lower right  of the desktop as shown： What is the significance of this icon？ （）

• A、 It indicates that the client adapter is not associated to an access point or another client.  
• B、 It indicates that the radio of the client adapter is disabled.
• C、 It indicates that the client adapter is associated to an access point or another client， but the  user is not EAP authenticated.
• D、 It indicates that the client adapter is associated to an access point or another client， that theuser is authenticated if the client adapter is configured for EAP authentication， and that the signal  strength is poor.
• E、 It indicates that the client adapter is associated to an access point or another client， that the  user is authenticated if the client adapter is configured for EAP authentication， and that the signal  strength is fair.
• F、 It indicates that the client adapter is associated to an access point or another client， that the  user is authenticated if the client adapter is configured for EAP authentication， and that the signal  strength is excellent or good.