Answer:
D. 0.3 M
Explanation:
                       NH4SH (s)    <-->       NH3 (g) + H2S (g)
Initial concentration        0.085mol/0.25L       0         0
Change in concentration   -0.2M                +0.2 M     +0.2M
Equilibrium        0.035mol/0.25 L=0.14M       0.2M      0.2M
concentration
Change in concentration (NH4SH) = (0.085-0.035)mol/0.25L =0.2M
K = [NH3]*[H2S]/[NH4SH] = 0.2M*0.2M/0.14M ≈ 0.29 M ≈ 0.3M