综合写作：
Beavers are medium-sized mammals that inhabit rivers and streams throughout North America and parts of South America and Europe. They are best known for building dams, or structures made of twigs and branches that block the flow of water. Beaver dams provide numerous benefits to both people and the environment; as a result, efforts are being made to increase the beaver population in many areas.
One of the benefits of beaver dams is that they increase the amount of water available to communities. Without dams, water would flow through rivers without stopping. Dams create a barrier in the river that slows the flow of water and keeps large quantities of it in the area. Not only do dams keep rivers full, they also allow water to seep down into the soil, penetrating land far away from the river bed. This increases the water supply for both townspeople and farmers, something which is especially important in times of drought.
Second, beaver dams significantly increase biodiversity(the variety of plants and animals) in the areas where they are located. Because dams help to store and retain water, there will be more vegetation, including grass, shrubs, and other plants alongside rivers with dams. Wildlife in turn are attracted by the vegetation, which provides food, shelter, and other benefits for a number of species, including birds, elk, and deer.
Finally, beaver dams can turn a river into an ideal habitat for certain types of fish. Since the water that accumulates behind a dam flows very slowly compared to water in other parts of the river, fish that prefer slow-moving water can inhabit rivers where there are beaver dams. This slow-moving water also provides a protective habitat for fish during the winter due to its relatively stable temperature.
学术写作：
Your professor is teaching a class on Biology. Write a post responding to the professor’s question.
In your response, you should do the following:
- Express and support your opinion.
- Make a contribution to the discussion in your own words.
An effective response will contain at least 100 words.
Dr. Diaz
In the next two weeks, we are going to be studying how biological discoveries have affected our lives. Research in biology provides us with a better understanding of how our bodies work. As an introduction to this topic, I would like for you to discuss among yourselves this question: What is the most important thing a person can do to maintain good health? Please explain why you think so.
Claire
I feel very strongly that a good diet is the most important factor in maintaining good health. Eating good, healthy foods, especially green vegetables, gives your body the materials it needs to stay strong. Good nutrition is the key to good health.
Paul
Most people don’t visit the doctor for regular checkups. Sure, if they feel sick, like they go, but that’s not enough. During a yearly exam, a physician can help a patient address health issues before they become a larger problem. So I think preventive doctor visits are key to good health.
