This analogy asks us to fill in P and Q so that Water is to P as Food is to Q. The trick is to first name the exact relation joining Water and P, then test each option to see if Food and Q follow that same relation.
Only the first option keeps a consistent relation: lacking the item in the first word produces the named feeling in the second word, for both halves of the analogy. So P = Thirst and Q = Hunger.
Let's summarize:
So the correct combination is P = Thirst and Q = Hunger.