Which of the following combinations of three different physical quantities P, Q, R can never be a meaningful quantity?

Which of the following combinations of three different physical quanti

1.	Which of the following combinations of three different physical quantities P, Q, R can never be a meaningful quantity?
Answer» `PQ-R` `(PQ)/(R )` `(P-Q)/(R )` `(PR-Q^(2))/(QR)` ANSWER :C