The drawing depicts sigmund freud's famous iceberg analogy for the structure of personality. which letter labels the personality structure that doesn't develop until about age 5 or 6, and represents a person's conscience?

It would be the letter than contain this word: preconscious

According to siegmund, preconcious is the memory or thought that lies under unconcious mind but are not directly suppressed by us.
Preconcious allow us to develop the concept of empathy but does not necessarily make us able why a certain action is considered as good or bad

The repetition of initial consonant sounds is called alliteration