Prototyping is most useful for requirements determination when:

A) user requirements are well understood.
B) communication problems have existed in the past between users and analysts.
C) possible designs are simple and require an abstract form to fully evaluate.
D) multiple stakeholders are involved with the system.
E) data are not readily available.

B
Explanation: B) Often, both parties want to be sure that system requirements are as specific as possible to avoid communication problems.
CL