Text for the items from 13 to 20.

1 Carbon dioxide is a compound in which two oxygen atoms are connected to a carbon atom. At normal temperatures it is

a colourless gas that exists naturally in the Earth’s atmosphere. The air that we breathe has about 0.03% of carbon dioxide in it.

Carbon dioxide is an important part of the carbon cycle and essential for life on Earth. Without it temperatures on our

4 planet would be very low.

Plants use the sunlight and take up the CO2 in the atmosphere to produce energy and oxygen. This process is called

photosynthesis.

7 The gas is also produced when fossil fuels are burned. Carbon dioxide that has been stored for millions of years in coal,

oil and natural gas is set free. Living creatures produce carbon dioxide when they breathe out. It is emitted from volcanoes and

hot springs. Deforestation sets carbon that is stored in trees free.

10Carbon dioxide is an important greenhouse gas. Light that enters the atmosphere it is converted to heat. Higher amounts

of CO2 make the atmosphere denser and keep it from getting out. CO2 is a gas that is highly responsible for global warming.

Since the Industrial Revolution of the 1800s the amount of CO2 in our atmosphere has risen by 40%.

13Throughout the centuries carbon dioxide has been in balance. Now more carbon dioxide is being produced than can be

absorbed by nature.

Carbon dioxide is used in various industries to produce food, chemicals and oil products. It is especially common as a food

16 additive and is added to beverages to give fizz to sparkling wine and water. It is also responsible for a beer’s foam.

As a pressurized gas carbon dioxide is used in fire extinguishers because it does not burn. Put in cartridges it can be used

to inflate bike tires. In its solid form CO2 is called dry ice. It is used for cooling fresh food or ice cream. Liquid carbon dioxide is

19 needed to remove caffeine from coffee.

Oceans are carbon sinks. They absorb more than 25% of all the carbon dioxide that people emit into the atmosphere. As

a result, the ocean’s water is becoming more acidic. This change affects the food chain and all sea organisms.

22 Although carbon dioxide is not poisonous in normal amounts it can kill you if there is more than 10% in the air.

High concentrations can lead to dizziness, bad sight, breathing problems as well as a high blood pressure and an increased

heartbeat. High levels of CO2 occur when there is not enough fresh air in a room.

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Based on the text, judge the following items.

The word “amounts”, in “Higher amounts of CO2 make the atmosphere denser” (lines 10 and...