A Cisco Aironet 1020 controller-based access point has been connected to a Catalyst 3550-24 PWRSwitch. However， when it is powered up， the access point fails. What has caused this problem？（）

• A、access point has not been initialized with the primary controller
• B、switch port is not enabled
• C、switch does not support 802.3af
• D、access point does not support 802.11h
• E、incorrect switch power supply