A student floating in seawater with 5% of their volume above the surface implies their body density is less than that of seawater, which allows them to float with part of their body above water.
When a student floats in seawater, which has a density of 1030 kg/m³, with 5% of their body volume above the surface, it can be inferred that their body density is less than the density of seawater. This is because the extent to which an object is submerged depends on its density relative to that of the fluid. Since the student floats and is not completely submerged, the student's body density must be less, allowing for some volume to be above water. If the student's density were greater than that of seawater, they would sink. Thus, the correct inference is B) The student's body is less dense than seawater.