Final answer:
In response to an active bomb threat, a member should secure and control the immediate area (option B), which ensures safety and allows law enforcement to manage the situation.
Step-by-step explanation:
Upon responding to an active bomb threat, the member should secure and control the immediate area where the explosion occurred, which is option B). It is crucial for the safety of all individuals nearby that the area is quickly cleared of non-essential personnel and that law enforcement and explosive ordnance disposal (EOD) teams have unrestricted access to handle the situation. The entire building may be involved if the threat is not localized while securing the surrounding neighborhood is typically beyond the initial response scope, although it may become necessary depending on the severity and scale of the threat.