Introspection cannot be used to study
a. topics that are strongly colored by emotion.
b. mental events that are unconscious.
c. processes that involve conceptual knowledge.
d. events that take a long time to unfold.

The correct answer is letter C.

Explanation:  Introspection is the term that characterizes the action of making an intimate and reflective analysis of oneself.

This action requires a deep reflection on the lived experiences or what is most intimate within.

answer; pentagon papers, vietnam draft-resistor, james dean, american revolution;

answer; the above statement is (true);