综合写作
题目原文：
The Northern Pacific sea star, which is native to the coasts of Japan, Korea, and China, has recently appeared thousands of kilometers away. Because this sea star now threatens to harm marine ecosystems in new and distant areas, scientists are currently investigating ways of controlling the spread of invasive Northern Pacific sea stars.
Quicklime
One method of reducing Northern Pacific sea star populations is by administering a poison called quicklime. Quicklime in its powdered form can be spread over large areas of the seafloor invaded by the sea stars. While quicklime destroys sea stars, it does not harm commercially important mollusks, such as oysters, scallops, and mussels, which are cultivated on the seafloor in many waters.
Introducing Parasites
A second strategy is to introduce parasites that naturally control the spread of Northern Pacific sea stars in their native habitat. One major reason why Northern Pacific sea star populations are flourishing in distant waters is the absence of natural enemies, such as parasites. In their native environment, male sea stars are infected by parasites that specifically attack their reproductive system. If these parasites became established in distant waters, invasive Northern Pacific sea star populations could be significantly decreased.
Treating Ballast Water
A third measure involves sterilizing ballast water. Ships that have unloaded their cargo take aboard some amount of sea water as a weight and balance stabilizer. This sea water is referred to as ballast water. Sea star larvae (immature sea stars) float freely in the sea and are often taken up in ballast pumps. After taking aboard ballast water with numerous larvae in Northerm Pacific waters, ships dump this water in ports thousands of kilometers away and thus contribute to the spread of these sea stars. If ships treated their ballast water with chemicals before releasing it in a different location, Northern Pacific sea stars could be prevented from spreading to new areas.
题目音频：
学术写作
Dr. Achebe
More and more, online shopping is becoming the primary way that many people obtain everyday goods. But what are the ramifications for the society in which we live? On the one hand, online shopping has advantages-for example, I can make a purchase without ever leaving my home. However, with fewer people shopping at local shops, in some places, these establishments are having a hard time competing. Do you think that online shopping is, on the whole, affecting society?
Andrew:
I think that online shopping has had negative impacts on society. In my city, many local stores have shelves filled with various products that you can find in online stores. This has forced some of them to closedown, which not only affects the amount of tax revenue generated in our local community but also impacts the number of job opportunities available to the community members.
Kelly:
It’s unfortunate that some local stores are forced to close down, but that’s the nature of competition. As consumers, we benefit greatly from online shopping due to lower prices. Even if l find a physical store that can compete with online sellers in terms of pricing, I am still likely to make the purchase online because it means i don’t have to spend money on transportation to the store.
