The answer is (c): the water level in the tank will be the same, as seen in the photograph at the right, and in an mpeg video by clicking your mouse on the photograph at the right.
In the original configuration the water level in the tank is displaced by the weight of water in the beaker, as well as the weight of the styrofoam block and the beaker. In the final configuration, this water has been added to the water in the tank. This has the same effect on the water level in the tank as having that water displaced by its weight pushing down on the water in the tank.
