To examine one's own thoughts and feelings

Answer: Option D

One word substitute is Introspection.

Meditation: the action or practice of meditating.
Retrospection: the action of looking back on or reviewing past events or situations, especially those in one's own life.
Reflection: the throwing back by a body or surface of light, heat, or sound without absorbing it.
Introspection: the examination or observation of one's own mental and emotional processes.