Final answer:
The correct answer to the question is C. 70 kg, considering that the 42 kg water weight is part of the total body weight and that the total must be greater to include other body components.
Step-by-step explanation:
A person who has 42 kg in water weight would have a total body weight that is more than 42 kg because the water weight is only part of the total body weight.
Calculating the average density of a person can help us understand how much of their body would be submerged when floating. For instance, if a 60.0-kg woman floats in freshwater with 97.0% of her volume submerged, her average density can be calculated.
Moreover, knowing the density of the human body, which is generally less dense than salt water and roughly equal to the density of freshwater, we can infer that the body is almost entirely submerged when floating in water.
Therefore, the correct answer is C. 70 kg, assuming that the person's density allows them to float with part of their body above water, similar to the aforementioned examples.