2. (b) That's probably wrong, although there are insufficient facts to be sure. Generally, if there is a reasonable means of escape or evasion of the restraint there is no false imprisonment. But the available means of escape must be one that the plaintiff could reasonably be expected to take. It should not involve physical danger, humiliation or perhaps even embarrassment.
If B was aware of the existence of an unlocked fire escape, and could safely use that exit without danger, humiliation or embarrassment, then there would be no false imprisonment. But if B was not aware of the fire exit, she may have believed there was no escape, and this would change the outcome.