At what temperature does the density of liquid increase to 56.96 lbs./ft3?

The correct answer is based on an understanding of how the density of liquids, in this case, a refrigerant, changes with temperature. As temperature decreases, the density of most liquids tends to increase because the molecules become more closely packed together.

In this scenario, the question is asking for the specific temperature at which the density reaches 56.96 lbs./ft3. The choice indicating 39 degrees is correct because, at this temperature, the density of the refrigerant is known to be 56.96 lbs./ft3 based on established data.

When considering the other temperature options, either they reflect lower or higher densities based on known properties of refrigerants throughout their temperature ranges, leading to incorrect selections. Understanding the relationship between temperature and density is crucial in applications such as industrial refrigeration, as it can significantly affect system efficiency and performance.