Consider the Interconversion of a Molecules (Shaded Spheres)and B Molecules

Consider the interconversion of A molecules (shaded spheres) and B molecules (unshaded spheres) according to the reaction A ⇌ B.Each of the following series of pictures represents a separate experiment in which time increases from left to right.
-Which of these experiments has resulted in an equilibrium state?

A) all of the experiments except experiment (1)
B) all of the experiments except experiment (2)
C) all of the experiments except experiment (3)
D) all of the experiments except experiment (4)