在家里，自立的你应该[ ] A．自己的事情自己做，有困难多向长辈请教 B．自己的

自相关函数一定是（）函数。

A、奇

B、偶

C、周期

D、非周期

Tom Brennan was working in a Philadelphia office building when he noticed a black bag. The bag contained a book.

This chance discovery ended a 12day search by the Library Company of Philadelphia for a historical treasure -- a 120-page -diary kept 190 years ago by Deborah Logan, “a woman who knew everybody in her day,” James Green, the librarian told the magazine America Libraries.

Most of the diary is a record of big events in Philadelphia. It also includes a description of British soldiers burning Washington D.C. in the war of 1812. She describes President James Madison on horseback as “perfectly shaking with fear” during the troubled days. George Washington, she writes, mistook her for the wife of a French man, and praised her excellent English.

The adventure of the lost book began September 4 when Cory Luxmoore arrived from England to deliver the diary to his ancestor (祖先) to the Library Company, which he and his wife considered to be the best home for the diary.

Green told American Libraries he had the diary in his possession “about five minutes” when Luxmoore took it back because he had promised to show it to one other person. On returning to his hotel after showing the precious book to Green, Luxmoor was shocked to realise that he had left it in the taxi.

Without any delay, Green began calling every taxi company in the city, with no luck. “I've felt sick since then,” Luxmoore told reporters.

According to Green, no one has yet learned how the diary came to the office building. Tom Brennan received a reward (奖励) of $1 000, Philadelphia gained another treasure for its history, and Luxmoore told reporters, “It's wonderful news. I'm on high.”

51. This article mainly tells about the story of _______.

A. a lost diary                                           B. Deborah Longan

C. Cory Luxmoore                                   D. the Library Company

52. From the text, we learn that the diary is now owned by _______.

A. Tom Brennan                                             B. an unknown person

C. a Philadelphia magazine                       D. the Library Company of Philadelphia

53. Philadelphia is thought to be the best home for the diary because _______.

A. it was written in Philadelphia                 B. it tells stories about Philadelphia

C. people in the city are interested in old things

D. the British and the Americans once fought in Philadelphia

54. Which of the following shows the right order of what happened to the diary?

a -- Tom Brennan found the book in an office building.

b -- The book was shown to James Green.

c -- Cory Luxmoore arrived from England.

d -- The book was left behind in a taxi.

A. a, b, c, d         B. c, b, d, a                 C. a, c, d, b                        D. c, a, b, d

55. What did Cory Luxmoore mean when he said “I'm on high”?

A. I'm rich                    B. I'm famous                    C. I'm excited                    D. I'm lucky

保健食品生产企业应制定原料的（），采用“先进先出”的原则，对不合格或过期原料应加注标志并及早处理。

A、生产日期 

B、储存期 

C、保存期 

D、包装日期 

E、最佳食用期

具有缓解充气位、缓解后保压位、制动位、制动后保压位四个作用位置的是（）。

A.自动制动阀

B.单独制动阀

C.分配阀

D.中继阀