You are troubleshooting a problem with a cisco 7920 wireless ip phone on a standalone wlan. the phone rings but， when you Answer ，the call is dropped. What may have caused this problem？（）

• A、publicly secure packet forwarding is enabled.
• B、the minimum data rate is not set to 11 mbps.
• C、an address resolution protocol is enabled.
• D、the access point is set to the least congested channel.