CWNA Wireless Network Administrator

Answer - B - Fresnel zone should not be blocked more than 40 percent to maintain a reliable communications link.
Key Takeaway: Fresnel zone is the area around the visual line-of-sight that radio waves spread out into after they leave the antenna. This area must be clear to keep the signal strength. Fresnel Zone is an area of concern for 2.4 GHz wireless systems. Any more than 40 percent infringement into the Fresnel zone is likely to make a link unreliable.