Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 39 to 45. Greenhouse gases trap heat in the atmosphere. This natural process is what makes the surface of the Earth warmer, making it possible for living things to survive. Greenhouse gases can be classified into four major groups. · Carbon dioxide (CO₂) comes from the burning of fossil fuels and biological materials. When it is absorbed ...

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 39 to 45.

Greenhouse gases trap heat in the atmosphere. This natural process is what makes the surface of the Earth warmer, making it possible for living things to survive. Greenhouse gases can be classified into four major groups.

· Carbon dioxide (CO₂) comes from the burning of fossil fuels and biological materials. When it is absorbed by plants, it is removed from the atmosphere.

· Methane (CH₄) is the by-product of the production and transportation of coal, natural gas and oil, agricultural practices and the decay of organic waste.

· Nitrous oxide (N₂O) is emitted during agricultural and industrial activities. It also originates from wastewater treatment. It is absorbed by certain types of bacteria or destroyed by ultraviolet radiation or chemical reactions. Methane is removed from the atmosphere through natural processes in soil and chemical reactions in the atmosphere. Methane’s lifetime in the atmosphere is much shorter than carbon dioxide, but it is much more efficient at trapping radiation.

· Fluorinated gases (CFCs) have their origins in a variety of household, commercial and industrial applications and processes. Fluorinated gases are in smaller quantities than other greenhouse gases, but they are the most potent and longest lasting ones. Fluorinated gases are removed from the atmosphere only when they are destroyed by sunlight in the upper atmosphere.

Each of these gases remain in the atmosphere for a different amount of time, ranging from a few years to thousands of years. They remain long enough to become well mixed, meaning that the amount measured in the atmosphere is roughly the same all over the world, regardless of the source of emission.