A single 802.11g access point has been configured and installed in the center of a square office. A few wireless users are experiencing slow performance and drops while most users are operating at peak efficiency. What are three likely causes of this problem?（）
- A mismatched TKIP encryption
- B null SSID
- C cordless phones
- D mismatched SSID
- E metal file cabinets
- F antenna type or directio