this should be B -

Higher gain antennas spread the signal on the horizontal plane, which creates a larger cell that also picks
up more noise. This results in a lower signal-to-noise ratio (SNR), which increases the packet error ratio.
SNR is defined by the following two criteria:
• Signal—The radiated energy transmitted from one radio that can be received uninterrupted by
another radio. For Wi-Fi, this means that the transmitting radio is sending 802.11 protocol packets
that the receiving radio is able to decode.
• Noise—Transmitted energy in the frequency range of the receiving radio that cannot be decoded by
that radio.
The larger the difference in energy between the protocol packet and the background noise, the better the
reception of the protocol packet and the lower the packet error rate and bit error rate. Coverage area
design involves using channels to create the lowest possible packet error rate while maintaining a high
call capacity.
Higher gain antennas can also reduce the number of calls on a Wi-Fi channel because of the increased
coverage area. For voice, a ceiling-mounted antenna is preferred over a wall-mounted patch because the
human head and body attenuate 5 dB of the signal (see Figure 9-1). Ceiling mounted antennas are better
positioned to avoid more of this head and body attenuation than most wall-mounted antennas.