综合写作：
Argentavis magnificens, the largest bird to have ever inhabited Earth, lived six million years ago in the southern part of South America that roughly corresponds to modern-day Argentina. The bird, which is known only through fossil remains, weighed up to 68 kilograms. There is some debate about whether this bird was able to fly or whether it had lost its ability to fly at some point during its evolution.
First, there is the problem of lifting off into the air. Based on its skeletion, the bird’s total wingspan was nearly seven meters. Wings this long would have hit the ground if the bird had tried to lift off from a standing position. Modern flying birds have wing-to-body proportions that allow them to take off without hitting the ground with their wings.
Second, even if the bird had managed to lift off, it does not appear to have had enough muscle strength to make continuous flight possible. As large as it was, the Argentavis does not appear to have had sufficient muscles to keep its huge wings moving. It is highly improbable that its muscles could move its wings fast enough to keep it in the air for extended periods.
Third, according to the theory of evolution, animals only have abilities that give them an advantage in their struggle to survive. Flying would not have given this giant bird any advantage. It did not need to fly in order to escape predators, because of its size it had no predators. It could not use flying to hunt because it would have been such a clumsy and inefficient flier that it could not possibly have captured enough food. The bird, therefore, probably lost the ability to fly during its evolution.
听力音频：
学术写作：
Your professor is teaching a class on Education. 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 our discussion this week, we are going to discuss the subject of course selection during high school. As we all know, education plays a crucial role in shaping our future. While the right courses can be challenging given the variety of options, but there are certainly key courses that could be more beneficial. As students in the secondary school stage, or in high school, which course do you think is the most important and should be made compulsory? And why do you think so?
Claire
In my opinion, math should be a compulsory course in high school. Nowadays, people are too reliant on using apps and machines; technological advancements have weakened their math skills in daily life so math should be a compulsory subject. It is beneficial for students’ future financial planning and other arrangements.
Andrew
I would argue that biology should be made compulsory. Biology is very commonly used. Without knowledge of biology, students might not even know how to use medications. Studying biology helps us with everyday things, like understanding basic health care and making good choices about our environment.
