The correct answer is D. All the above.
The speed of sound in dry air at 0°C is 343 meters per second, which is equal to 1190 kilometers per hour. The speed of sound varies with temperature, increasing by 2.4 kilometers per hour for every degree Celsius rise in temperature. One Mach is equal to the speed of sound in a given medium. Therefore, all of the statements in the question are correct.
The speed of sound is a physical property of a medium that measures how quickly sound waves travel through that medium. The speed of sound depends on the medium through which it is traveling, as well as the temperature and pressure of the medium. In general, sound travels faster through solids than through liquids, and faster through liquids than through gases. The speed of sound also increases with temperature.
The speed of sound is important in many fields, including physics, engineering, and medicine. In physics, the speed of sound is used to study the properties of waves and to calculate the properties of materials. In engineering, the speed of sound is used to design and analyze structures and to predict the propagation of sound waves. In medicine, the speed of sound is used to diagnose diseases and to monitor the progress of treatment.