食品放置久了就会腐败变质，主要原因是 A．细菌的呼吸作用 B．动物的取食作用 C

阅读下面短文，从短文后方框中所给的五个句子中选出四个，分别填入文中相应的序号后，使短文语义连贯，结构完整。
Reading is very important to help you learn English. This book provides not only different kinds of English but also a good way to check your reading ability.
小题1:_______.
Part 1 is Messages. In this part somebody wants to send information in writing to somebody else. There is a test on timetable and a test on text messages.
小题2: ________. You will find some descriptive writing in this part. There are descriptions of clothes and of a computer.
Part 3 is Places. In this part, too, many different kinds of English are shown, some informal and some formal（正式的）. There is the informal English of a holiday postcard. There is also the formal English in a thank-you letter.
Part 4 is People. In this part all the tests are about people. 小题3:________. There are also some biographies（传记）about famous people. There is a job application as a model to help with your writing, as well as testing your reading.
小题4:________, or you can do all the tests with a formal or informal text.

A．Part 2 is Things B．There are four parts in the book C．There is another part about Nature D．You can do these tests in any order you like E. For example, there are some letters between friends