Read The Water Cycle. The water cycle is a natural phenomenon. It has implications for all of the living creatures it affects. Water is drawn up into the atmosphere as it evaporates from the ground, rivers, lakes, oceans, flora. and fauna. This water collects in our atmosphere. Then, it gathers together in concentrations that form clouds. Eventually, the clouds become too dense with water. This causes precipitation to begin and fall back down through our atmosphere. It lands on the Earth's surface as rain or snow. This precipitation then travels through the ground, plants, rivers, lakes and oceans. From there, it evaporates back up into the air to begin the cycle again.

Water is restorative in nature. A threat to the natural restorative nature of the water cycle is acid rain. Acid rain is caused by certain gas emissions in our atmosphere. Volcanoes release some of these gases naturally. However, the primary cause of these harmful emissions is human activity and industry. Large factories and gas-powered vehicles send harmful pollutants into the air. As these harmful gases are released into the atmosphere, they are caught in evaporated water molecules, causing acid clouds to form. The gases are also picked up by precipitation that falls from the clouds. The gases mix with the water molecules to form acids, which then fall from the sky as rain or snow. As air pollution continues, acid rain in the water cycle worsens.

Acid rain can poison plants and be harmful to animals. It is so strong that it slowly breaks down buildings and stone. The acids break down building materials. They can also burn the leaves of plants. Acid rain can even change the chemical make up of soil, making it toxic to plant life. It can also lower the productivity of farms and crop yields. As rivers and lakes become more acidic, acid rain destroys fish and aquatic life. Ocean creatures with exoskeletons are at risk of acidic waters. The acid weakens and dissolves their exoskeleton. There are many harmful effects on the water cycle caused by acid rain.

Which of the following best describes the structure of the article? (2 points)

a
Cause and effect

b
Chronological order

c
Compare and contrast

d
Problem and solution