Within a plant, photosynthesis is critical. It provides cells with the glucose they need for
energy. Photosynthesis is important for another reason, too. It's part of the flow of carbon
through organisms and the environment. This cycle, known as the carbon cycle, is essential
for life on Earth. It includes several processes that are occurring all the time. When plants
photosynthesize, carbon is removed from the atmosphere as carbon dioxide. When animals
and plants use cellular respiration, carbon is released into the atmosphere as carbon
dioxide. Organisms that die and are buried for millions of years turn into fossil fuels, which
are made of carbon. When humans burn those fossil fuels, carbon is released into the
atmosphere as carbon dioxide. Without enough carbon dioxide in the atmosphere, the
planet would be too cold. But too much carbon dioxide contributes to the warming of the
planet that could make it too hot to survive.
Based on the passage, what is one reason that the carbon cycle important?
A It adds carbon into the atmosphere whenever the level begins to drop too low.
B
It helps maintain a level of carbon in the atmosphere that is neither too hot nor
too cold.
с
It removes carbon from the atmosphere whenever the level begins to become
too high.
D
It releases carbon into space, preventing it from building up in Earth's
atmosphere.