Which of the following statements concerning air temperature is true?

The statement that "They are all correct" reflects the truth of all the individual statements regarding air temperature and its properties. Each statement provides valid insights into the behavior of air and its interaction with temperature.

Cold air being heavier than warm air is rooted in physics. The molecules in cold air are closer together and move slower than those in warm air, which causes warm air to rise above cold air. This principle is fundamental in meteorological phenomena, including convection currents.

Warm air holding more water vapor than cold air is tied to the concept of saturation. When air is warm, its capacity to contain water vapor increases significantly due to the kinetic energy of the molecules, allowing them to hold more moisture before condensing. This is a fundamental aspect of humidity and weather patterns, influencing things like precipitation and cloud formation.

The third statement regarding wind creation also aligns with atmospheric science principles. When air moves due to temperature differences, it creates wind. The unequal heating of the Earth's surface leads to variations in air pressure, resulting in air movement, which we experience as wind.

Since all of these statements correctly describe important aspects of air temperature and its effects, asserting that all statements are true is justified.