综合写作：
To help address the problem of global warming, scientists have proposed an ingenious plan: using rockets to release large amounts of sulfur dioxide in Earth’s atmosphere. Sulfur dioxide would form hazy clouds that reflect sunlight. The clouds would reduce the overall amount of solar heat reaching Earth’s surface, which would have a cooling effect on Earth’s climate. However, critics point out that this plan has serious flaws.
First, the released sulfur dioxide would create some negative environmental effects. In the atmosphere, sulfur dioxide undergoes chemical reactions and becomes sulfuric acid, which eventually combines with water vapor in the air and forms acid rain. Acid rain has been proven to harm animals, damage forests, destroy crops, and corrode structures made of stone.
Second, this plan would be too expensive to implement. Launching rockets with sufficient amounts of sulfur dioxide to have any effect on Earth’s climate would cost about a billion dollars. And since the sulfur dioxide would eventually leave the atmosphere, we could not do this just once—we would have to launch rockets with additional sulfur dioxide every year or two, costing a billion dollars each time.
Third, the effects of seeding the atmosphere with sulfur dioxide would be very limited in scope. Although the procedure has not been done yet, scientists have observed the effects of a similar process: the spraying of sulfur dioxide into the air when volcanoes erupt. A volcano eruption in 1982 put 20 million tons of sulfur dioxide in the air, and afterward, the average global temperature for the next year declined only by half a degree Celsius.
学术写作：
Instructions: Your professor is teaching a class on education. Write a post responding to the professor’s question. In your response you should:
- express and support your personal opinion
- make a contribution to the discussion in your own words
An effective response will contain at least 100 words.
Dr. Diaz
This week we will discuss issues faced by secondary school administrators. I’m referring to schools for teenage students. One such issue is students who change schools. Students change schools for many different reasons, the most common being a family move. On the discussion board, I want you to exchange ideas about what schools can do to make the transition to a new school easier for teenagers.
Paul
I think schools should assign new students a fellow student who can help them adjust. The “student buddy” can do things like make sure the new student can find the cafeteria or the right classrooms. For new students, it’s a lot easier to ask a fellow student a question rather than ask a teacher or the principal.
Claire
I would require new students to sign up for some school club or activity that meets outside of class. That way, new students would have an easy way to meet other students in a friendly environment. It would give them a group to immediately identify with.
