One of the Following Activities Can Complicate Critical Thinking and Re-Framing

One of the following activities can complicate critical thinking and re-framing - which?

A) Working in new, alien contexts.
B) Having the choice to apply a theory that is previously unknown to the analyst.
C) Long and in-depth studies of theory/perspective that you like and identify with.
D) Long and in-depth studies of theory/perspective one initially finds difficult in.