综合写作：
Sauropods were plant – eating dinosaurs from the Jurassic and Cretaceous periods notable for their enormous size; the largest species may have reached 50 meters in length and weighed up to 100 tons. It has been suggested that the evolution of gigantism (enormous size) in sauropods was caused by environmental factors. Scientists have proposed several theories identifying environmental factors that may have been responsible.
High Levels of Atmospheric Oxygen
One theory suggests that sauropods reached gigantic sizes thanks to very high levels of oxygen in the atmosphere. According to this theory, the atmospheric oxygen content during the Jurassic and Cretaceous periods was significantly higher than it is today. The high oxygen levels led to improved respiration (breathing) in sauropods. Improved respiration allowed sauropods to grow extremely large.
Plentiful Food Sources
A second theory holds that the large size of sauropods was the result of the availability of plentiful food sources. During the Jurassic and Cretaceous periods, the climate favored the rapid growth of lush forests. Sauropods had virtually unlimited supplies of plants to feed on. So the theory goes that without the limitations of food resources that normally control body size, sauropods evolved larger and larger bodies to become giants.
Warm Climate
According to a third theory, the main factor that allowed sauropods to evolve large bodies was the very warm climate of the Jurassic and Cretaceous periods. Animals living in warm climates do not need to generate as much body heat as animals living in cold climates do. Sauropods could therefore use most of the energy they obtained from food to grow and maintain body tissues rather than to generate body heat. This allowed sauropods to grow larger than animals in other periods.
学术写作：
Instructions
Your professor is teaching a class on sociology. Write a post responding to the professor’s question.
In your response you should:
- Express and support your opinion.
- Make a contribution to the discussion in your own words.
An effective response will contain at least 100 words.
Doctor Achebe
This week, we are discussing the social psychology of sports. We have learned that sports often have positive psychological effects on athletes, such as the members of sports teams. But how can we describe their effects on other groups of people, such as sports enthusiasts or sports fans? Consider the following question: when people spend a lot of time watching sports or following their favorite team, does it have a negative effect on their lives? Why or why not?
Claire
I agree that focusing on sports too much can have negative impacts. For example, some people who like watching sports on television have few other interests. In fact, it seems like watching sports is all they’re interested in. I sometimes find such people annoying because they care too much about things that don’t matter.
Paul
I am not sure what we mean by spending “a lot of time” following sports. But following sports has helped me in life when I first met one of my best friends, Dayne. I started a conversation with her by saying something about a sports team I liked. Then we moved to other topics. But sports were a great conversation starter.
