I would go with adjective on this one.
Answer:
The chemical and physical functions of the brain and how they work.
Explanation:
Psych is related to the mind and conscioussness, bio and biology are concerning the physical being and body. Therefore, combining them would be talking about both, hence how the brain (psych) works on a physical (bio) level.
I cant see the rest of the passage, but im taking a guess that it is no.2!
The word thoughtless provides a clue to the meaning of insensitive because the defenition of insensitive means showing no feeling or concern about anyones feelings
Mr Lo is a doctor and he takes care of sick people
