Final answer:
Phoebe is exemplifying the fundamental attribution error when she assumes Rachel must be very emotional for crying, without considering situational factors.
Step-by-step explanation:
The individual demonstrating the fundamental attribution error is option a) Phoebe who sees Rachel crying in the bathroom and assumes that Rachel must be very emotional. This scenario shows Phoebe making an internal attribution about Rachel's behavior without considering the possible situational factors that might have influenced Rachel's emotions. Unlike option b) which exemplifies self-serving bias, option c) which demonstrates an individual's self-assessment, and option d) which reflects the actor-observer bias, option a) aligns with the concept of the fundamental attribution error because it involves judging another person's behavior based on dispositional factors while disregarding situational contexts that could be influential.