综合写作：
The two main groups of mammals are marsupials and placentals. Marsupials include animals such as kangaroos and opossums; placentals include many familiar animals such as cats, antelopes, and monkeys. A typical distinguishing feature of marsupials is the pouch: a fold of skin on the belly of marsupial females that provides protection to newborn babies. Marsupials are often regarded as being more primitive and less well adapted to various environmental challenges than the placentals are. There are good reasons for such a view.
First, while a placental newborn is typically well developed after a relatively long period of embryonic growth inside its mother’s body, marsupial young, called joeys, are born after a relatively short period of embryonic development. As a result, joeys are very immature. Many of their internal organs are not fully developed, and their immune system is not functioning well enough to prevent infections. Joeys are thus much more vulnerable than fully developed placental newborns.
Second, adult marsupials seem inferior to placentals in certain physiological abilities. For example, internal body temperatures of many marsupials vary more than those of many placentals. This suggests that marsupials lack the ability to efficiently control their internal body temperatures. Maintaining a stable internal temperature is important for keeping physiological functions at optimal levels.
Third, in regions such as South America where marsupials and placentals live together, the marsupials include fewer species and have smaller populations than the placentals. This indicates that when marsupials and placentals are placed in direct competition, marsupials are less successful at surviving and adapting to various ecological roles. The marsupials are dominant only in Australia, but that is because placentals did not live in Australia until quite recently. In other words, the marsupials have thrived in Australia only because they did not really have to compete against the placentals there.
学术写作：
Instructions: Your professor is teaching a class on public policy. 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
Many areas are trying to reduce fossil fuel consumption because such fuel causes pollution and may contribute to climate change. To this end, some local governments want to find ways to encourage more people to use electric vehicles. In preparation for a class discussion on this issue, please post a response indicating what policy or initiative you would recommend that governments implement to encourage more use of electric vehicles. Please explain why you chose so.
Kelly
I live in an apartment building and would have difficulty charging an electric vehicle at home. I think that governments should offer financial support to encourage places such as shopping districts to install a large number of charging stations, maybe even free ones, that the public could use.
Paul
People in my city often deal with long commutes in heavy traffic. But if my local government could set aside lanes on high – traffic roadways that only electric cars could use, that might encourage people to purchase such a vehicle because they would have shorter and easier commutes.
