The answer is (a): the surface of the lighter liquid in the left side of the U-tube will be above that of the water in the right side of the tube, as can be seen in the unmasked photograph at the right.
Because the fluid in the left side of the U-tube is lighter than water, it will float on the water. Because it is lighter than water a taller column of the lighter liquid will be required to create the same pressure at the bottom of the U-tube, as seen in the photograph. Notice that the clamp holding the U-tube covers the boundary between the water and the lighter liquid, adding to the mystery.
