For the reaction $2A(g) + B(g) \rightleftharpoons 3C(g) + 4D(g)$ Three moles each of $A$ and $B$ were taken into a $1\; L$ flask. which of the following is always true when the system attains equilibrium?

Question

(a) [A] = [B]

(b) [A] < [B]

(c) [B] = [C]

(d) [A] + [B] < [C] + [D]