Answer: A - Sound waves must move through a substance.
Sound waves require a medium to travel through, such as air, water, or solids, and cannot travel through a vacuum, such as the empty space of outer space. This is because sound waves are mechanical waves, which means they require particles to vibrate and transfer energy from one point to another.
When a sound is produced, such as by a vibrating object, it causes the particles in the surrounding medium to vibrate, creating a series of compressions and rarefactions in the medium. These compressions and rarefactions then propagate through the medium as a sound wave, transferring energy from the source of the sound to our ears.
In the vacuum of space, there are no particles to vibrate, and so there is no medium for sound waves to travel through. Therefore, sound waves cannot travel through space. However, electromagnetic waves, such as light and radio waves, can travel through a vacuum because they do not require a medium to propagate.
