Final answer:
The scale will still register the same reading because it measures the weight of the water displaced by the submerged object, despite the object not touching the bottom of the beaker.
Step-by-step explanation:
The students predict that the reading of the scale will not change because the combined body is suspended in the water and does not touch the bottom of the beaker. However, this prediction is incorrect. When an object is submerged in water, it exerts a buoyant force upwards, which is equal to the weight of the water displaced. Despite the object being suspended in the water and not touching the beaker, the weight of the displaced water exerts this buoyant force on the object, which in turn is transferred to the beaker and thus to the scale. Consequently, the scale will still register the weight of the beaker and the water, along with the effective weight (weight minus buoyant force) of the suspended object, resulting in an unchanged reading.
As bathroom scales measure weight but are calibrated to display mass, the weight force they measure on Earth would not be the same as on the Moon due to the difference in gravitational pull. The mass of the object would remain the same, but the force (displayed as mass) would differ because the gravitational acceleration on the Moon is much less than that on Earth.