Longitudinal wave: this wave produces vibrations in the direction it moves, that is, it pushes the particles in the medium towards their direction of propagation.
Unlike another type of wave that is the transverse wave, which produces vibration in a direction perpendicular to its direction of propagation.
So the wave mentioned in the statement is a longitudinal wave because the displacement of the particles is in the direction of the wave.
An example of this type of wave are sound waves, which are transmitted by vibrations in the particles of the medium (like air) in their direction of the movement of the wave.
If you count the number of seconds between the flash of lightning and the sound of thunder, and then divide by 5, you'll get the distance in miles to the lightning: 5 seconds = 1 mile, 15 seconds = 3 miles, 0 seconds = very close. Keep in mind that you should be in a safe place while counting.
The amount of each gas that can dissolve in the ocean depends on the solubility and saturation of the gas in water. Solubility refers to the amount of a dissolved gas that the water can hold under a particular set of conditions, which are usually defined as 0o C and 1 atmosphere of pressure.