综合写作：
Some scientists have proposed an interesting way to slow down global climate change: they want to increase the growth of phytoplankton in Earth’s oceans by fertilizing the oceans with iron dust. Phytoplankton are tiny, ocean – dwelling plants that can absorb great amounts of carbon dioxide (CO₂). Since carbon dioxide contributes enormously to global warming, increasing phytoplankton by iron fertilization is expected to slow global warming. However, there are many potential problems with iron fertilization.
First, iron fertilization may not be very effective. So far, only very few experiments have shown that iron fertilization leads to increased absorption of atmospheric CO₂ by phytoplankton. In addition, the increases in CO₂ absorption detected in the experiments were quite small. This leads many experts to think that full – scale iron fertilization would be just as ineffective.
Second, the quick growth of phytoplankton can lead to dangerous increases in environmental toxins. Some phytoplankton produce toxins that are relatively harmless in small amounts but can be very dangerous when produced by a large enough population. The toxins kill some species of fish, which hurts the fishing industry. They also cause other species of fish to be poisonous for human consumption, which causes many people to become sick. If we implement iron fertilization, we can expect this to happen much more often.
Third, seeding the oceans with large volumes of a nutrient such as iron could upset the oceans’ ecological balance. We do not know how the various ocean organisms will react to an iron – rich environment. Some may thrive in it, while others may suffer. In the long run, iron fertilization could change the plant and animal composition of the ocean ecosystems; some species may even become extinct as a result.
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 personal opinion
- make a contribution to the discussion in your own words
An effective response will contain at least 100 words.
Dr. Achebe
College tuition fees are rising steadily, putting financial pressure on many families. One proposal is that government should cover tuition costs so that anyone can attend college for free. What do you think? Should government pay for college and make higher education free? Please explain your viewpoint.
Claire
I believe college should be free for all students. This would promote fairness and access to education, giving underprivileged students more opportunities. Everyone deserves a chance to pursue higher education, regardless of their financial situation. Free tuition would open doors for many capable students who currently can’t afford the high costs of attending college.
Paul
I don’t think college should be free for all. That could attract many students who aren’t genuinely interested in learning, overcrowding classes. It’s better to keep some cost so students are motivated, and classes aren’t too large, which hurts the quality of education.
