综合写作：
Several species of cypress trees, which can grow in wetlands and shallow water, produce unusual structures called knees. Unlike roots, cypress knees grow above the ground. They are strange formations that extend upward from the trees’roots into the air. While the function of roots is well established, the function of knees is still unclear, but scientists have several hypotheses.
Oxygen absorption
First, knees may help the trees’ roots absorb or take in oxygen. Plant roots require oxygen for important cellular functions, and the soil in the watery habitats where cypress trees often grow is low in oxygen. Roots of plants growing in low-oxygen soil must often obtain oxygen from another source. For example, mangrove trees, which also grow in soil that is underwater, are known for having above-ground roots that absorb oxygen. Like the roots of mangroves, cypress knees may take in oxygen from the air and deliver it to the deeper roots.
Additional stability
Second, knees may help cypress trees stand firmly in the soil, making them better able to remain securely in place when exposed to high winds or strong water currents. The fact that the cypress has knees in addition to a network of roots may provide additional stability, allowing the tree to anchor itself well in the soil. Cypress trees may need this additional support due to the softness of the wet soil in which they grow.
Methane release
Finally, knees grow on trees in areas where methane gas exists in the soil. The knees are in direct contact with the soil infused with methane, which is of no use to trees. Therefore, the function of knees may be to release methane gas from the trees’ roots into the air. The fact that measurable amounts of methane have been detected in the air above the knees supports this idea.
学术写作：
Your professor is teaching a class on Economics. 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
We are discussing recent trends in consumer behavior. One trend is a decrease in the use of cash money. Consumers don’t use physical money to pay for things as much as they used to. Online shopping has a big impact on this. But even when shopping in person, more people are using credit cards, cash cards, and phone apps to make purchases. So do you think the decrease in using cash is positive or negative ？Why?
Claire
I think it’s great. I avoid using physical money. The main reason is that I don’t want to carry around a wallet stuffed with paper bills and coins. I carry my mobile phone with me anyway, so why carry two things when I only need one? Using my phone to pay for things in the store is a huge convenience.
Kelly
I think it’s negative. It’s easier to keep track of your spending when you use cash. When paying with cards or phone apps, it’s easy to ignore how much you spend and go over your budget. But with physical money, you are more aware of your spending, and if you run out of cash, you can’t spend any more!
