Answer is both (b) and (d).
Explanation;
Equilibrium constant is written as a ratio between concentrations of products and reactants.
The equilibrium reaction is
A(g) ⇄ B(g)
Hence, the equilibrium constant can be expressed as
K = [B(g)] / [A(g)]
If there is more B, then A should be less. Hence, K value would be more than 1.
Hence, according to the given choices, K = 4000 and K = 1 x 10⁶ can be taken as correct answers.