Quotation marks, also called 'inverted commas', are of two types: single and double. British practice is normally to enclose quoted matter between single quotation marks, and to use double quotation marks for a quotation within a quotation:
The oceans absorb the sun's heat, transferring it to the atmosphere and distributing it around the world via the ever-moving ocean currents. This drives global weather patterns and acts as a heater in the winter and an air conditioner in the summer.
Currents are the circulation system of oceans, which move water from place to place. These movements are controlled by gravity, wind, and the rising and sinking of water in different parts of the world, due to varying temperature. Temperature has a great effect on the density of water. As water warms, it expands and becomes less dense, causing it to rise to the surface.