Let us Rename the Tuples and write the given relation R(A,B,C,D,E,F) (just for simplicity i am renaming)
Now lets write FS set
A,B,C->D,E,F { Doctor,Patient,Date determines the remaining three attributes }
E->F ( Treatment code determines charge)
So candidate key wil be ABC. SO Fd,A,B,C->D,E,F is in BCNF as ABC is key.
Lets check E->F
Clearly ABC-> E ->F is transitive dependency so it is not on 3nf. {Non prime transitively determined by key}
But E->F is not a partial dependency as E is not proper subset of candidate key.ABC->DEF is already is in BCNF and E->F is in 2nf so i can say overall my relation is in 2nf.
So, b is the correct answer here.