What statement about 802.11 WLAN bridges is true?

What statement about 802.11 WLAN bridges is true?
A . WLAN bridges only work in the 2.4 GHz frequency band and they support only SISO communications
B . WLAN bridges must use a channel with acceptable SNR at both transceivers to maintain the desired data rate bi-directionally
C . WLAN bridges may support MIMO communication, but only if used in the GHz frequency band
D . WLAN bridges must be implemented such that no interference occurs on the channel anywhere between the two endpoints used to establish the bridge

Answer: A