The reaction `A + B hArr C + D` is studied in a one litre vessel at `250^(@)C` . The initial concentration of A was 3n and that of B was n. When equilibrium was attained, equilibrium concentration of C was found to the equal to the equilibrium concentration of B. What is the concentration of D at equilibrium ?
A. (A) `n//2`
B. (B) `(3n-1//2)`
C. (C) `(n-n//3)`
D. (D) `n`
