Which of the Following Statements Provides the Most Serious Obstacle

Which of the following statements provides the most serious obstacle to the use of introspection as a source of scientific evidence?

A) When facts are provided by introspection,we have no way to assess the facts themselves,independent of the reporter's perspective.
B) Introspection is only effective for children,because children have not yet learned to inhibit their own self-reports.
C) Introspection is a valid method only if the person doing the introspection goes into a trancelike state.
D) The process of reporting on one's own mental events is too slow to be scientifically useful.