The correct option is B Great-aunt
Given, P Q R S + T
Here, S + T means S is the mother of T.
R - S means R is the brother of S.
Q R means Q is the father of R and S as well.
So, Q will be the maternal grandfather of T.
Again, P Q means P is the sister of Q.
Clearly, P is great aunt of T.
Hence, option (B) is the correct answer.