What does this mean?

You are sitting in an airport preparing to use a free WLAN. When you look at the connections in
your Windows 7 wireless client, you see a network name and three boxes with a yellow shield.
What does this mean?

A.
You cannot connect to this WLAN.

B.
An open ad hoc network is nearby.

C.
The WLAN in the airport is open.

D.
A secure ad hoc network is nearby.

E.
A secure WLAN is in the airport.

F.
You must provide a username and password to access the WLAN in the airport.