What do you think is the reason behind this?

Sandra is conducting a penetration test for pass4sure.com. She knows that pass4sure.com is using wireless networking for some of the offices in the building right down the street. Through social engineering she discovers that they are using 802.11g. Sandra knows that 802.11g uses the same 2.4GHz frequency range as 802.11b. Using NetStumbler and her 802.11b wireless NIC, Sandra drives over to the building to map the wireless networks. However, even though she repositions herself around the building several times, Sandra is not able to detect a single AP.
What do you think is the reason behind this?

A.
Netstumbler does not work against 802.11g.

B.
You can only pick up 802.11g signals with 802.11a wireless cards.

C.
The access points probably have WEP enabled so they cannot be detected.

D.
The access points probably have disabled broadcasting of the SSID so they cannot be detected.

E.
802.11g uses OFDM while 802.11b uses DSSS so despite the same frequency and 802.11b card cannot see an 802.11g signal.

F.
Sandra must be doing something wrong, as there is no reason for her to not see the signals.